So I had ATT for a little over a month and figured if I changed over to tmobile I could save over $40 a month in the bill. So I've got my 1.1.1 phone unlocked and got my sim today from tmobile with the Total internet package. My problems lies in this, the 1st time I put the sim in, it worked. I even made a phone call to a friend and was all happy. Then I turned the phone off, and back on to have it not work sense. I've done a lot of reading on the forums but I can't even find out what's wrong with the phone, let alone why it's not working.

I see a button in the settings called Carriers, I typed internet2.voicestream.com and I see a T-mobile listed, but it wont let me select it.

Help?