There are such features in selected mobile, where you can use two SIM cards instead of one. All you need to do is to buy a cover accommodating two SIM cards. This gives you the advantage of holding pay-as-you-go and a pre-paid SIM cards, for example. This may be useful for your office and personal use. In normal circumstances, you can remove your SIM card from your present handset and carry with you and choose to use it with the line of GSM phones available. If you misplace your SIM card, you will be required to inform your service provider immediately to that effect, and follow the instructions given. You may be liable to pay charges for issuance of a duplicate SIM card.

When you buy a GSM phone, it comes in an unlocked state and it can work with any SIM card from any service provider, provided you are using it for GSM bands. It is a matter of slipping-in that SIM card in your phone, activating it and start using it. But, when you enter into a service contract with a service provider, which stipulates that you should be with this particular service for a definite period of time, a mobile handset is usually offered free with the SIM card, where the handset is given to you in a locked state. This would mean that the phone will not work with any other SIM card than the one given to you. You will need to stay with your service provider till the end of the term and after that the service provider may help you to unlock your phone. There are ofcourse ways to unlock a locked handset, which becomes a violation of the contract that you have signed with your service provider. A locked phone features a SIM lock in reality. In such a handset, you will not be able to use any other SIM card other than the one which has come along with your handset. That is the reason why it is sometimes termed as a SIM locked phone.

Any SIM card may be used with an unlocked GSM phone. For a pre-paid SIM card, you do not need to enter into any contracts and more-over there would not be any bills to pay at the end of the month. For instance, if you are traveling abroad and wish to visit a few countries in your trip, you can buy an International SIM card, for the benefit of saving up-to 80% of your cost in calls. This card will give you the facility of free incoming calls, no matter where it generates from, and outgoing calls at local rates. When you make calls to your home, you do not pay the roaming charges, as you would do if you had carried your regular mobile with you. But in this instance, you have to make sure that you have a quad band GSM mobile phone, in order that you may use the handset effectively when you are abroad. If not, you will need to rent one unlocked quad band GSM phone. To know more about the matter, visit www.planetomni.com/RENT_INFO.shtml For SIM cards visit www.planetomni.com/FAQ_sim.shtml

Since unlocking a locked phone under contract is not taken to be legal, it is always preferable to buy an unlocked phone from the market and you will have the choice to get your SIM card from the service provider who gives you the best deal. Also, this avoids your expenses that you would incur in getting locked phone and trying to have it unlocked from such vendors offering to do the job for you. There is a pitfall here too in buying an unlocked handset. You should be able to distinguish between a carrier unlocked phone and a factory unlocked one. The main draw-backs of carrier locked phones are -

 Use of pirated software to unlock a locked phone.
 In such phones, you may observe that even if you try to connect with a correct IP address, to your provider’s WAP or GPRS services, the phone may not allow the setting, may not comply with your request or automatically will try to connect to another service provider.

Therefore, it is always a good choice to buy factory unlocked mobile handsets from known vendors. For more details visit www.planetomni.com/

When you buy a prepaid SIM card for your unlocked GSM phone, there are a few things that you should remember:

Barring some of the countries, unlocking a locked phone, when under the contract terms, is seen to be a breach of contract. But in countries like Poland, the law says that the service providers are not allowed to word their contracts with the customers, which forbids them to remove the SIM locks in their handsets.

For more details on how to use SIM cards in an unlocked mobile phone, visit www.planetomni.com