So I got an unlocked iPhone and signed it up for a T-Mobile FlexPay account. I took it home this afternoon, and I noticed that in addition to the T-Mobile network, my iPhone was also picking up the AT&T network. If I leave the phone on automatic detection, it seems to alternate between the two (obviously picking the strongest one). I can receive calls and send texts on either, it would seem. So what in the world is going on here?! :S Am I roaming? Does T-Mobile have some kind of partnership with At&t in my area (Central Arkansas)? I'd like to know, because sometimes At&t's network is a lot stronger and using it would be awesome, but I don't want to rack my bill up. Any thoughts?