Yep... just popped in the AT&T Sim Card. Annoying message and VERIZON splash screen on start up, but the phone worked straight up - no problem. Mine, FYI, is a Galaxy S5.
Blew compressed air into the earpiece and Boom! Best fix ever. Now if all that crap from early in the thread could be removed it would be the best thread ever. Really happy to have the proximity sensor back to working. Thank you!