Iphone 4 software unlock on Ios7?

I have an iphone 4 at&t and it fell in the water so i said that its lost and now that its fixed i can't take it to at&t and i installed ios7 on it. But it doesn't read my sim (country georgia) it says: invalid sim. So is there a program to software unlock my iphone? Is there a free one ( i'm kinda broke). Can you search for the cheapest? I'm not used to this kind of software.

What's happened here is because you claimed it as lost they've blacklisted the IMEI number (think of it as the phones passport ID number) to make it unusable if somoenes finds it. Ring up AT&T and tell them you found it.

OR

If you've time and patients you can always wait for a jailbreak for iOS 7 to come out, you can unlock your phone with that through cydia. But there's no release date as of yet.