I'm having problems getting a reliable 3G connection on my Samsung Galaxy S2. I have a grandfathered unlimited data plan and other discounts I'd like to keep which is why I bought this phone unlocked instead of getting a subsidized phone. The 3G connection wouldn't work after just putting in the sim card, I had to google some APN settings to see what would work. My data plan is called Media Net Unlimited or "GPRS WAP UNLTD DOM - MN21" on my bill. I found the following setting which I tried: [I'll try to post in next message due to spam filter] The settings only partially work. The 3G connection may work anywhere from a few minutes to an hour or two. But then the 3G icon disappears, a no icon (circle with a line through it) appears for a second along with a message on the bottom of the screen that says "refreshing sim data". After a couple seconds the message disappears and the 3G returns. But if I try to do anything again it drops the connection again within a minute. When I'm on wifi or I disable the data connection, I don't get the "refreshing sim data" message at all and the phone works normally for voice. Also, I am completely unable to send or receive MMS messages ever. My signal strength is good and if I put my sim back into my old phone (Nokia N75, also unlocked and purchased independently of at&t) the data connection works just fine. I can send/receive MMS messages, use the built-in browser or opera browser, and access email. Any idea what maybe causing the "refreshing sim data" message and disappearing 3G? Are there better APN settings I can try? Is AT&T blocking my phone based on IMEI or something?