I can get a $50 a month plan on ATT. $450 minutes, 2 Gig of data. 23% corporate discount. But that doesn't include text messaging.
T-Mobile has some great rates, including a $2 a day plan (2g data). If you don't use it on a particular day, you are not charged. I am currently trying to test them out with an unlocked ATT phone, I live outside of town and I am not sure if I would have better service with a T-Mobile branded phone. It my understanding that WalMart (Straight Talk) and another company who's name begins with an S, use the T-Mobile nework.
I should also note, that I am currently using a off contract BB 9810 ( and paying
full contract prices) on AT&T and doing some test onT-Mobile. I am wanting to upgrade, but I have never been so confused and not known what I want to do in all my life. And it's been like this for about six months.