Re: how to switch phone to use with different carrier
First the phone must be unlocked by the p;resent service provider. If the phone is paid for or you have fulfilled any contract, they should do this with no problem. If you owe on the phone or are still under contract you'll have to work that out wiith them or maybe your new provider wil pay it off. If you try to just take of with the phone while owing money, they will blacklist the phone's IMEI number, making it unusable.
Second, the phone must be compatible with your new provider of choice. You'll need to know the phone's sub-model number. Then go to this site to find out if the phone will work:
WillMyPhoneWork.net - Check if your phone works on a network