GSM (Global System for Mobile Communications) is a cellular standard of service used across the planet. Most of the world's cellular service is GSM making it relatively easy to travel from country to country with your own cell phone and number.

The service used predominantly in the United States is called CDMA (used by Verizon). GSM is quickly catching up in the US thanks to T-Mobile and Cingular/AT&T, although it is expensive to make or receive while travelling overseas.

The SIM (Subscriber Identity Module) card also known as a "smart chip" is basically the "brain" of the phone, providing cellular service as well as many other functions including call history, voice mail and text. SIM cards are the size of a credit card but they have a pop-out chip about the size of a postage stamp which fits into all modern GSM phones. The SIM is embedded with circuitry and when inserted into a GSM phone provides wireless phone service on a particular GSM network.

A locked phone is one that has been altered in order to use only one particular cellular provider (for example: T-Mobile, 02, Vodafone or Cingular etc). An unlocked phone is one where any restriction has been removed and can therefore you can fit any SIM card.

Many handsets are not locked at all. Some handsets however are "locked" by the supplying network to operate with their specific network SIM card.

The easiest way to find out if your handset is locked is to borrow a different network SIM card from a friend and fit it to your handset. If you see any of the following messages your handset is probarbly locked:

• SIM Card Not Accepted
• Enter Restriction Code
• Enter Special Code
• Enter Subsidy Code
• Enter Subsidy Password

If you need your handset unlocking, you have 3 options:

1. Visit our unlocking partner site to unlock your handset on-line (there is a charge for this service).

2. Visit you local retailer or service centre to unlock your handset. Prices will vary so we advise you to call in advance and ensure they can unlock your particular model.

3. Contact your usual network provider. They can usually provide this service but it tends to be more expensive than the options above and may involve sending your phone away.

Remember, once your handset is unlocked you are free to use a GSM SIM card as many times as you like - so you can continue to make massive savings on your calls in the future!

It is not illegal!

Some prepaid SIM cards have a security mechanism in place that requires the user to enter in a PIN (Personal Identification Number) code every time the phone is turned on. When a PIN code has been assigned it is important not to forget this code. If you enter the PIN code incorrectly into the phone 3 times in a row then your phone will display a 'Blocked' message. When this occurs you will then be required to unblock your phone using the PUK (Personal Unblocking Key). If you enter the PUK incorrectly 10 times in a row you will block your SIM card indefinitely and you will have to purchase a new one.

All phones have a different set of procedures to enable PIN locks so you may have to consult your phone manual for full details.

Turn the phone over and remove the battery cover and battery. Remove the existing SIM Card and replace it with the GO-SIM, making sure to use the locking mechanism of your phone to hold it in place.

Store your usual SIM card safely so that it can be re-fitted at a later date.

Global SIM cards allow a user to make and receive calls in multiple countries without paying expensive roaming charges - usually saving up to 85% compared with using your usual service while traveling. The GO-SIM Global SIM card works in 175 countriesusing over 400 local Network Operators making it a robust solution for multi-country travel.

The call charges are straightforward and published on our website so that you always know how much a call will cost you. Because this is an international service, base call rates and initial credit is in USD ($) and may be converted to other currencies on this website.

The service is prepaid - so you add call credit in advance with no hidden charges - no monthly or annual fees and no call set-up or access charges.

You are automatically notified when your credit is low so that you can top-up securely again with go-sim. And best of all, unused call credit never expires - so you can use the service year after year!

Not at all. Calling cards are used to make outgoing calls via public phones or landlines so you can be billed. Of course, nobody can call YOU if you have a calling card.

The Global SIM is an international mobile service based out of Estonia and therefore the SIM mobile number has a +372 prefix. For US customers, we also provide a US number.

The cost to call the Global Sim will depend on how much your network provider or fixed line carrier charges to call an Estonian mobile. For your ease, we have made some Gateway or Toll Free numbers available which make the cost of calling the Global SIM much cheaper.

The Global SIM service operates in 175 countries around the world on over 400 networks. This means that in many countries you can actually make and receive calls on more than one network. The Global SIM will normally automatically select the strongest signal but it may be possible to manually select another network if required.

The available network list will be displayed in your handset if you select 'manually search networks' (or something similar) via your handset menu. Whichever of the available networks you choose, the call rates will always be the same.

Simply click on the Rate Calculator so see the cost of calls in all countries covered by the service. When you get your Global SIM card there will also be a table of call rates included with the user guide - however, although rates don't change often, always check the website for the most up to date information.

We recommend that you always keep a copy of your phone contacts. There are many low cost applications available which can be installed on a PC which allow this to be done. When you save a contact on your usual phone, it can be stored to either the handset memory or to the SIM memory so we suggest that you make sure all important that both memories are backed up.

You now need to transfer contacts to your new Global SIM card. A really easy way of doing this is to use the GO-SIM Data Bank. This is a SIM card reader/writer on a key-ring that acts as a portable data bank for your mobile phone numbers without the need for a PC. Simply, insert your SIM card to make a copy or backup and transfer your contacts to your new GO-SIM card.

You can buy this as an accessory when you purchase your GO-SIM card or look in the Accessories section under Products on the website

The Global SIM card can hold up to 250 phone numbers and 20 SMS messages. It is a Java Card 2.1.1 and has a 64K EEPROM

The GO-SIM Global SIM card is pre-activated - so no need to do anything, simply fit into your compatible GSM handset and start using the service

Unlike many other similar providers, unused call credit on your GO-SIM Global SIM card never expires so you can use the service year after year

YES. You can call and text anywhere in the world - there are no hidden charges; our rates are the same for calls to fixed or mobile numbers

Text messages can be sent in two ways - either via the keypad as you would normally or via the GO-SIM menu. If you use the GO-SIM menu the cost of each text message is greatly reduced. Click on the Rate Calculator to see all call charge

Yes, the GO-SIM Global SIM card is GPRS compatible and in some countries 3G is also supported.

Coverage currently extends to over 80 countries with multiple networks being available to connect to in some providing a great solution to data on the move.

Users will need to configure their handsets to take advantage of the service by installing settings provided by GO-SIM either manaually or sent over the air (OTA). You can send the data settings OTA for your specific handset my logging into your SIM card account in MyGO-SIM. If you handset isn't covered by the OTA service, you may still be able to confiure it manually using the following information:

APN: send.ee
User name: (your full Global SIM mobile number)
Password: (leave blank)

Data rates are per 100KB and are shown by clicking on the rate calculator. You require a minimum airtime balance of $9.00 to use data services on the Global SIM card.

The GO-SIM Global SIM card uses a clever process called 'call back'. It is a little different to how you would usually make a call on your mobile phone, but is really easy to use. Effectively, after dialling the number you want to call, our system calls you back within seconds and your handset will ring - answer it as usual and that is it, you are connevted.

Every time you make a call:

1. Dial the number using the full international code (even if you are in that country).

For example, to dial the UK GO-SIM number 0845 6583410 from anywhere in the world you will need to dial 00 44 845 6583410

2. Your handset will display a Calling... message
3. Within a few seconds your handset will ring
4. Answer the call as usual and you are connected

If you see the message 'Call barred', 'Restricted number' or 'Check operator services' it is because some handsets hanve software that means the way you can make a callrequires a different dialling procedure. This is called GO-SIM Menu Calling.

To make calls using this method, first locate the GO-SIM Menu option in your phone:

• Nokia: the last item on the Main menu
• Sony Ericsson: in the Connectivity menu
• Motorola: in the Office Tools menu
• Samsung: in the Applications menu
• Siemens: in the Main or Extras menui
• If your phone uses icons, look for the GO-SIM icon.

To call the Global SIM you must always dial the full international mobile number (including prefix) - for example, dial 00 372 followed by the number 00 372 53112345.

For your ease, we have made available gateway numbers (or Toll free numbers for our US customers) which make the cost of calling the Global Sim much cheaper. Simply call the gateway number and follow the voice prompts. For more details click on 'Gateway numbers' or 'Toll free numbers' in the Support section.

The GO-SIM Global SIM card can be bought from Best Buy stores in the USA and at Thomas CookForeign Exchange Bureaux at London Heathrow Terminal 5 and Manchester Airport in the UK and on Thomas Cook Airlines. Additional retaillers are constantly being added and will be shown on our website.

Either look at the 'Buy Products' section or select your destination from our the countries in the drop-down list. This will take you to the right product for your needs. If you are traveling to more than one country, check that all destinations are covered from the country list on the product page or by using the Rate Calculator. You can also compare products in a simple table of high level features and benefits.

You may also want to check our website special offers where you will find Global SIM cards with extra call credit or with handset bundles at special online only prices.

When you have made your selection, click on the 'Add to basket' button. Add any other items you might need, eg any additional airtime credit or a handset, to your shopping basket. In particular, look out for the 'May we also suggest' items below the shopping basket which often contain special offer products.

When you have finished shopping, select your preferred delivery option and click on the 'Checkout' button. You'll then just need to complete the quick registration form online, followed by your secure payment details. A secure online account is then created for you so that when you return (e.g. to add more call credit) it is quick and easy to make additional orders.

Once completed, you will receive a notification via email and your order will be shipped to your door before you travel.

You can also call us at any time on the number displayed on the Contact Us page in the Support section of the website or click on the 'Live Support' button to chat online to a member of the GO-SIM team.

With the Global SIM card, you are automatically notified when your credit is low so that you can top-up securely again by going to MyGO-SIM. And best of all, unused call credit never expires - so you can use the service year after year!

It depends where you are but we offer a next day delivery in many regions of the world. Firstly - make sure you choose your location using the 'site selector' drop down list at the top of our website. This will show products in the correct currency for you and also show the right delivery methods.

Now select 'Shipping' or 'Delivery' in the Support section to see all the relevent delivery information. You can select your chosen delivery method at the checkout stage.

For security reasons we can't deliver to airports but we can often deliver to your destination address or even hotel - please contact us to check.

No problem! Unlike many of our competitors, GO-SIM offer a range of contact methods which ensure you can always get in touch so we can help. If you can't see the answer to your query in our FAQ's, you can:

• Email us by clicking on the link in 'Contact Us' in the Support section.
• Have a 'live chat' with one of our in-house team of experts by clicking on the Live Support link in 'Contact Us' or;
• Give us a call:

In the UK on+448456583410

In the US on +18666046746

From outside the UK or US on +448456583410

30-day money back guarantee

We're so confident that you'll be happy with your new Global SIM card; we're offering a money back guarantee.

If you're in any way dissatisfied and wish to cancel your Global SIM service, you can contact the GO-SIM support team within 30 days of receipt and request a refund.

Losing your mobile phone is bad enough at any time but if you are far from home it can become much more than an inconvienience.

We recommend that you take out our SIM card protection plan when you purchase a Global SIM card. By simply selecting this at the checkout stage, your new Global SIM card will be protected and then if the worst happens, we will sort out a replacement card, transfer any remaining call credit and get it to you - fast.

MyGO-SIM is a website or portal designed specifically for GO-SIM users.

In MyGO-SIM, an existing customer can manage all aspects of their GO-SIM account, including:

• Add more airtime
• View calls made and received and produce reports
• Aent free SMS from MyGO-SIM to your Global SIM card
• Manage services such as voicemail and Voice2Email

To see what you can do in MyGO-SIM click here