Stupid question...please humor me. I'm a Verizon customer who jumped from the AT&T in a fit of anger/stupidity. Now I want to come back "home" to AT&T...but I traded my AT&T 4S to Verizon to purchase my current iPhone 5. Once & for all...can I use the Verizon iPhone 5 successfully on the AT&T voice/data network simply by switching SIM card to an AT&T one? I always thought since VZW uses CDMA & AT&T uses GSM technology, this isn't possible . Thanks.