Dead iPhone 3GS after ATT Unlock

Question

After I upgraded to a 4S, I kept my 3GS in hopes of someday unlocking it for my wife to use on t-Mobile. I was pleased to hear that ATT and Apple would provide an Unlock for out of contract iPhones. I got the unlock and everything went well for about week. Then one morning the 3GS was completely dead. I tried every reset and plugging it in to every type of charger. Still dead. I even took into the Apple Store and they said they couldn't do anything and would replace the 3GS for $150. This phone worked fine until the unlock, it may be coincidence but phone has never been dropped, or wet and is grreat condition. $150 is not an excessive amount if I can unlock it, which Apple says I can. I thought about replacing the battery for about $25 but Apple says that if I open it up the $150 is off the table. I would like to keep this phone since it is already unlocked and if I replace the battery could Apple really tell.
Any thoughts would be appreciated.

Answer 1

When ATT unlocked my iphone 3gs, it also turned into a brick. Completely died. I was traveling in Europe at the time, and wanted to switch out the sim card. When it died, boarding passes, reservations, directions, contacts, camera, etc, all gone. Totally aggravating. I had replaced a few parts over the years. It was old, but it still worked great, before the unlock.
Anyway, when I got home, I took out the battery and tested it, and sure enough it still had 3.5v. (I had replaced the battery maybe a year before.) And just for my own edification, I replaced the dock connector, thinking maybe that was the cause. Nope. Still wouldn't even be recognized on USB...let alone itunes.
When I went into Apple store, they confirmed that the phone was probably too old to support the software/change. Fair enough. But apparently, ATT unlocking phones has been problematic. Here's an recent example:
http://www.wsj.com/articles/SB10001424052702303559504579195881629809394
If it happens to you, I suggest demanding a credit from the carrier. ATT gave me $170. I bought a used, factory-unlocked GSM iphone 5s. swappa.com worked great. And going non-contract cut my mobile phone bill by two-thirds.