iphone 4s odd carrier behavior

[hackgoogle]

Hey guys, my sister recently bought an iPhone 4S (really dumb idea), and I've taken on the task of unlocking it. I have a Gevey S Ultra and I started with restoring the phone by downloading 5.1.1 from felixbruns.de, which was the current version of the phone. This is an ATT phone 100% sure. I called ATT earlier today for a factory unlock, but did not have the receipt for it. However, everything, including the IMEI, was in the records. When I restored the phone, I got a signal. Take note that there was no sim card in the phone, not even the holder. It connects to sprint and when I attempt to make calls, it says the phone is not authorized. Before the restore, it said no service, even with the Gevey S Ultra and the T-Mobile micro sim card. Can anyone provide insight into what might cause the problem? Worst case scenario, I have the warranty on it and can take it to the Apple Store. However, I want to know if it is my fault or Apple's fault. Thanks.

TLDR; new 4s, att confirmed, gets signal from sprint and is and connects to sprint without sim card in the phone after restore for no apparent reason, stock firmware