[Dimdem]

I've got a problem that I guess RIM is resolving, but I'm pretty new to the Blackberry universe and I'd just like a better understanding of the situation.
I got my unlocked BB 7290 off of EBay in December. I added the BB plan to my T-Mobile account, but couldn't get the data working. I went through tech. support at T-Mobile, but could never get the gprs in caps. Finally, T-Mobile went contacted RIM, and RIM did something---I was never told exactly what---which got it working. I then took an extended trip out of the country, and while I was gone I got rid of the BB plan so I wouldn't have to pay for it. I added it back when I got home, and had the same problem. I called T-Mobile again this week, and after a couple of troubleshooting steps, they again called RIM. I had a T-Mobile and a RIM support person on the phone at the same time. The T-Mobile person looked back at their old support notes, and in those notes it said that in December RIM had "updated me in the DWC." The RIM person said that he had never heard of "the DWC." Eventually, RIM called me back to say that they are going to send a new BB to one of their reps here, who will meet me and swap it for mine. They also wanted the name of the EBay seller who sold me the Blackberry. I'm just wondering if anyone can help me decipher what is going on here. How did RIM solve the problem the first time, and why can't they do it again? Was there something fishy about the BB I got from EBay? I went with a seller with a huge number of positive feedbacks.