Okay, so I've been trying to figure this out. When I get the tablet, I was in Florida, and the 3G worked fine. No problems whatsoever. Now that I get to my home in the NYC area, the 3G doesn't work at all. I've tested with 3 different AT&T sims and 2 different S7 tablets. Here's what I found out. Edge works. Edge will always work. The device has no problem initializing with the connection with the cell tower when GSM Only is set. After the device has initialized with the cell tower and has signal (Settings > Status > Mobile network state: Connected), you can switch to WCDMA (3G bands) Data will work, but dialing out will not. This is because voice is a different channel than radio on 3G. But if you remember, I said it worked in Florida. I believe this is because, in Florida, I probably didn't have HSPA (3.5G). I only had UMTS (3G). I have tried to disable hspa and try to get it to work on 3G only, but I haven't found a way. Are there any AT&T users on 3G that would like to report their findings?