Why did carrier name next to signal bars change?

Yesterday I was using my iPhone 3GS (iOS 6.0.1 on AT&T) and suddenly realized my carrier name next to the signal bars in the upper left corner had changed. It no longer shows AT&T. It shows a man's name. I have not done anything to change this. How could this have happened? I have not been roaming lately, and I have not been out of the country. I have seen postings about download third party software to change this, but I'm reluctant to download software I'm not familiar with. I have already power cycled it, done a hard reset, and done a network reset. Nothing has helped so far. Does anyone have an recommendations? I have read other postings that have stated the a system restore does not help either. Any ideas?