For some reason, I thought FlexPay went away when TMO came out with the Even More and Even More Plus plans late last year (around the time I left TMO) but looks like it is still around. It is important to the OP to know that he needs to ask about FlexPay, not PrePaid for TMO.
In the FAQ referenced above, TMO differentiates FlexPay from prepaid as follows.
| How is a FlexPay account different from a Prepaid account? |
With FlexPay you have the all the benefits of a monthly T-Mobile rate plan including Family Time and Unlimited plans. Simply pay in advance for each month of service. We will send you reminders so you will not forget.
Thanks Mama for keeping us all straight.