I have been using my iPhone 4 on T-Mobile for the last 2 months and have generally been happy with the service as I live in Minneapolis which has been refarmed. Last night I was in the immediate downtown Minneapolis area and I noticed my phone had actually switched to show AT&T service and the 3G logo. I didn't have any data service when I tried to access safari. I tried switching on/off Airplane mode and even rebooted the phone and it still kept pulling up AT&T. As soon as I got home (slightly out of the downtown area), T-mobile coverage came back. This morning I was again briefly in the downtown area and I was back on AT&T. I entered a building and I got T-mobile Edge service. I think several of the downtown buildings have internal nodes that aren't refarmed to 3G. As soon as I left the building I got AT&T again. This time I tried placing a call and it worked, but I had no data service. As soon as I drove out of the main downtown area, T-mobile 3G coverage came back. I have a few questions..... If T-mobile was down in the area, why did my phone move to AT&T instead of just saying "No Service?" Does T-mobile use AT&T for "roaming" backup in areas where they have no coverage? If so, is it normal that they only provide backup voice service and not data coverage? Strange that the 3G showed up, but yet I had no data. Is there any place to check for T-mobile service outages? I searched a bit on Google, but couldn't find anything. Could the fact that they are down be a sign that maybe they are doing some further upgrade work (rather than just being an unplanned service crash)? Maybe they are installing LTE in downtown Minneapolis? Seems strange that it was the immediate downtown area and as soon as I left on both NE side and SW side, the T-mobile coverage came back. I would guess they would want to upgrade downtown before other areas, but found it strange they would have a complete service outage while they do so.