It's two years since I trained people on this T-Mobile system, so take a pinch of salt, but...
It sounds as if you've been accepted, unless there's anything in the email about it being referred. It's meant to be an automated system, and so should work, but lots of thsi work has gone offshore so I had less contact with it as my time with TMobile progressed.
However, beware. T-Mobile may well have accepted you with a very low credit limit on your account - some have been as low as £50 in the past. What this means is that as soon as your amount outstanding goes over the credit limit your line will suspend until you make a payment. In some cases, although this is supposed to have been sorted out now, credit limits were almost the same as monthly payments, meaning one bill could send you over the limit. Two bills almost certqinly means you'll automatically suspend if you have a low credit limit. Even high unbilled calls during the month can bring the credit limit into play. Many TM staff will not tell you what your credit limit is until you're over it....