No you cannot. CDMA phones do not accept SIM cards.
Yes, you can flash a Verizon phone to ATT. However, you will also need to insert a Verizon SIM card into the ATT phone in order for it to properly work.
Yes, provided your ATT phone is SIM unlocked.
Yes as long as the phone is att and has a sim card slot
ONLY if the handset has been unlocked from any network.
No, you cannot use an AT&T GoPhone card in a Verizon phone because they operate on different network technologies. AT&T uses GSM, while Verizon uses CDMA. Therefore, a SIM card from AT&T will not be compatible with a Verizon device. To use a Verizon phone, you would need a Verizon SIM card.
Yes, provided your ATT phone is SIM unlocked.
That depends. Modern "World Phones", hybrid phones like the iPhone 4S that contain both a CDMA radio and GSM radio are technically possible, though Verizon won't activate any iPhone not purchased from them, since Verizon iPhones are "white listed" to the network and sim locked to prevent using them on domestic GSM carriers. On the other hand, you can take a "World Phone" such as a Blackberry from Verizon and use it with an AT&T SIM card, as long as it is SIM unlocked, chances are you will only use the GPRS network since most Blackberrys on Verizon were limited to that. Newer Verizon Blackberrys like the 9830 have modern GSM radios to handle more.
You can put any SIM card in an unlocked cell phone.
No, I've tried. You have to insert a special code. (3 tries and the phone locks down) You have to get another att phone.
any AT&T phone that can take that sort of sim card.
Verizon doesn't have sim cards. Only AT&T.
Buy a different phone or contact Verizon support.