^ You have a "set bill" with a contract :P
Boy, TMO has changed. I remember when I was 17 and signed a contract on my own, having no credit. People must have screwed up a lot since then

(I'm almost 23 now - old bag lol)
OP - there are a couple plusses to this. 1.) If you decide that you hate TMO, you're not in a super long contract with them. 2.) (I could be wrong, but this was how it was for me) This can build your credit if you pay ON TIME each month for the year contract. 3.) If you decide you like TMO and your year is up, you can go to a kiosk/store in the mall / strip mall and ask to sign with them for two years.
Really, truthfully, you'll like TMO if you haven't already had it. It's not crazy bad like other carriers.