In this section we list some commonly asked question and answers regarding GSM prepaid SIM cards and how they can turn a GSM world cell phone into an international cell phone with local rates. If you do not see your question listed here, please also view our other FAQ sections or feel free to contact us.

What is a SIM card (SIM chip)?

What is a prepaid SIM card?

Where is the cell phone number of my prepaid SIM card?

Will I have voicemail?

Are all incoming calls free? Does that mean "from anywhere"?

What is a PIN and PUK?

If the SIM card is prepaid then how do I add airtime?

When I add airtime does my GSM cell phone number stay the same?

What is an airtime voucher (recharge card, top-up card)?

If the purchase price for the SIM card is X dollars then why do I not get Y amount in airtime?

Can I purchase additional airtime with my SIM card?

Where can I purchase additional airtime?

Can I go to other countries (roam internationally) with my prepaid SIM card?

Are the incoming calls really free?

Do I keep the same phone number when I switch pre paid service for the next destination?

Can I call internationally?

Why does Telestial offer only one service provider in each country?

What is a SIM card (SIM chip)?

The SIM (Subscriber Identity Module) card is about the size of a postage stamp, with embedded circuitry on one side of its surface, which when inserted into a GSM cell phone provides cell phone service on a particular GSM network.

The SIM card provides you with a cell phone number and determines what features or services will be available to you, as a subscriber, on a particular GSM network.

SIM cards may be prepaid or postpaid, which requires a contract and usually bills monthly.

What is a prepaid SIM card?

A prepaid SIM card is a SIM card that activates a GSM cell phone without a contract and consequently requires the prepaid subscriber to purchase airtime credit prior to use.

There is often a service life of some duration typically 6 months after which the SIM card expires and a new one must be purchased for continued service. The service life may be extended indefinitely by purchasing airtime vouchers, which credit the prepaid SIM card with airtime.

As an example:

If you purchased a prepaid UK SIM card in January and did not add any airtime to the card at all it would expire after 6 months, in June. If however you added airtime in March then the SIM card would not expire until September and if you continue to add airtime then the card will continue to provide service indefinitely.

Where is the cell phone number of my prepaid SIM card?

The phone number of your prepaid SIM card is usually located somewhere on the packaging. The number printed directly on the SIM card is a SIM card number and is NOT the phone number. When you order a SIM card from the Telestial we provide with directions on the location of your GSM cell phone number within your SIM card packaging.

Will I have voicemail?

If voicemail is available it will be noted on the specific prepaid SIM card web page.

Are all incoming calls free? Does that mean "from anywhere"?

Incoming calls are free, regardless of where they originate from, for most GSM network operators overseas. However there are some exceptions and you should always check the web page of the specific prepaid SIM card that you are purchasing to verify that incoming calls are free.

If incoming calls are not free they are usually charged at the rates as domestic outgoing calls.

What is a PIN and PUK?

Some prepaid SIM cards have a security mechanism in place that requires the subscriber to enter in a PIN code every time the GSM cell 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 GSM cell phone will display a Blocked message on its LCD. When this occurs you will then be required to unblock your phone using the PUK code. All phones have a different set of procedures to unblock and you will need to consult your GSM cell phone manual when this occurs. Do not simply enter in the PUK code as this method never works.

If the SIM card is prepaid then how do I add airtime?

Talk time may be added by purchasing ‘Top Up' or recharge cards that are available in varying amounts of the local currency, depending on how much time you wish to add. You may ‘Top up' for as little or as much as you want; however, with some pre paid plans, the higher the value of the voucher, the cheaper your calls become. Most convenience stores, in metropolitan areas throughout Europe and Asia sell Top Up cards.

As an example: If you were to purchase a 25 Euro voucher, you would simply scratch of the silver peel to reveal a code that when punched into your GSM cell phone, will credit up your SIM card the respective amount of the denomination purchased.

To activate your talk time simply dial the number found on your recharge card, scratch the surface to reveal the voucher code and follow the automated instructions, entering the voucher code when prompted. Your talk time will then be automatically updated

Some carriers allow you to register your credit card with them and allow you to dial a local number from your phone to credit your SIM card with the credit card that you have placed on file, however the UK and Switzerland are currently the only 2 carriers with such a mechanism that accepts US bank based credit cards.

When I add airtime does my GSM cell phone number stay the same?

Absolutely. Your phone number is dependant on your SIM card and you add airtime to your SIM card by purchasing airtime vouchers. Do NOT purchase another SIM card when your airtime is depleted. Besides changing your phone number it is also an expensive way to add airtime.

What is an airtime voucher (recharge card, top-up card)?

An airtime voucher is a piece of paper often printed with its denominational value on one side and code that is covered and must be scratched with a coin to be revealed. Once exposed the code is punched into the keypad of your international cell phone crediting up your prepaid SIM card with the respective denomination of voucher that you purchased. The vouchers are face value and a 25 Euro voucher, as an example, will credit your SIM card 25 Euros.

If the purchase price for the SIM card is X dollars then why do I not get Y amount in airtime?

When you purchase the prepaid SIM card you are actually receiving a SIM card to insert into your GSM cell phone and that is what you, as a subscriber, are actually paying for. While you usually receive some airtime with your purchase this credit is subject to the local GSM network operator. Additional airtime, which may be purchased locally, is available at face value and as an example, 25 Euro voucher, will credit your SIM card 25 Euros.

Can I purchase additional airtime with my SIM card?

Additional airtime may only be purchased locally in the respective countries for each prepaid SIM card. However you may purchase as much additional airtime as needed for the Global prepaid SIM card.

Where can I purchase additional airtime?

You may purchase additional airtime at most convenience shops, petrol stations and basically any store selling a copy of the local newspaper.

Can I go to other countries (roam internationally) with my prepaid SIM card?

Many of the country specific or ‘local' prepaid SIM cards do offer some form of international roaming but there may be calling restrictions such as not being able to make international calls to any country other then the originating country of the SIM card. Also when you roam you will be charged a significantly higher tariff rate so do not expect free incoming calls and finally there may not be a mechanism for adding, as an example, airtime to a Australian SIM card in New Zealand, where they would only sell airtime vouchers for New Zealand SIM cards. For details on the services offered including roaming please visit the web page of the respective SIM card.

The Global roaming card from Swisscom provides the most robust coverage and consistent service for roaming internationally but the airtime rates reflect this.

Are the incoming calls really free?

Yes, all incoming calls are free and the caller simply pays their standard international long distance rate.

However there are some prepaid SIM cards for countries like the Ukraine and Hong Kong where incoming calls are not free but are charged at the domestic outgoing per minute rate.

Do I keep the same phone number when I switch pre paid service for the next destination?

No. You get a new phone number every time you swap SIM cards in your GSM cell phone. However, your phone number and voicemail will continue to function.

Can I call internationally?

Yes. As long as you have talk time available you can call anywhere in the world. You may use a local access number or dial directly from your cell phone.

Why does Telestial offer only one service provider in each country?

Telestial selected partners that provide the best combination of coverage area, quality of service, ease of use, and price. Because most of our customers are from ‘out of town', we selected carriers offering pre paid service that combined minimal maintenance with the greatest economy

Other FAQ pages of interest include:

GSM Mobile Phones

Satellite phones and areas outside of cellular coverage

Calling cards and how save even more money while abroad.

The Return-Call service, which is a bit more complicated then the calling card but can save you more money for the extra effort.

....and finally thee is the Glossary.