Cell Phone Help

Are GSM cell phone numbers locked to the IMEI# of the phone or is it locked to the SIM card? Im saving up for a better phone, cuz my Sony Ericsson T237 blows!! Iv been looking on eBay for cheap phones, since thats basically the only place you can find them at good prices without having to get a new plan. My idea is to get a new phone (hopefully one for Cingular, if not then Ill just unlock it) and if the phone number is locked to the SIM card then I can just take it out of my current phone, put it in the new one, and roll. If its locked to the IMEI# of the phone, then I have a little bit more trouble there, just Id have to go to a cingular store to have them set it up.

I think you'll find it's locked to the Sim Card.

I'm pretty sure thats the case anyway.

Thats what another person said on another board...Thank Ya

One more question...if I get a new cell phone (most likely gonna be the Nokia 3650/60)...and since its a bit bigger than most cell phones i was thinking of just switching the SIM card back and forth between my current fone and the Nokia. I figure thatd get kinda....awkward...so is it possible to lock 1 phone number too 2 different SIM cards if I buy a new one?