I've had my GSIII for about 3 months now, and is my first smartphone. A gift from my younger brother, who was working retail at a local Target store at the time and was able to finagle a dealer-exclusive AT&T discounted line. After some initial issues (had to swap out SIMs because the initial phone number was Texan and I'm in Cali) I've been enjoying the phone immensely.
However, something neither of us was expecting happened after he gave his two weeks and left the store: the service to my phone was inexplicably cut. I figured it had something to do with his leaving the store, though neither of us could explain why since we were paying the bill on-time. In any case, Bro suggested I should try getting the phone unlocked so I can use a non-ATT&T service with a comparable service and data plan to the retailer discount line I had before. After filling out an ATT&T online form we were approved and ATT&T sent us an unlock code. But it didn't work. Maybe the code was already used? We sent out for another, and the same code was emailed to us. At this point Bro took it upon himself to call customer service. I wasn't privy to all the details but it seems all they did was give him the runaround, saying they would call or email him back once they found out why the phone wouldn't accept the unlock code.
That was a month ago. And there my phone sits, unused. Wi-Fi works, at least. Can't make calls, though. I suppose I can just sign up for a new service under ATT&T, but my bro advises against it because I'll be paying double for the same service I had before; and he says we can get a better deal elsewhere. I'm new to the smartphone game and I don't know what I can do to salvage the situation. I post this here in the hopes that someone may be able to help or have an idea what I should try. Phone specifications:
SGH-i747
16 GB
Android 4.1.2
I'm not sure what other info would be necessary. And, oh yeah, ATT&T are now charging 300 bucks for breaking contract even though they were the ones who dropped our service. Yeah, this is why I kept out of the smartphone game until now.
tl;dr An officially-sanctioned ATT&T unlock code doesn't work for my SIII i747 model, what are my options?