How long have you had Verizon? Maybe since you've had Verizon, I dunno, maybe you've been late on it or any of your other bills, maybe your credit rating's gone down since you applied with Verizon... It could be alot of things..

Did you ever have service with T-Mobile in the past? Voicestream/Omnipoint/SunCom/Powertel or whoever the heck else's name T-Mobile goes by nowadays? You might also want to check out freecreditreport.com, you might find interesting things on there 😉

Ask the rep to figure out what is going on. It could be that there's an error in the system, you have a block on your credit, you have a past due t-mobile/voicestream/omnipoint account, or your credit has gone down severely since you activated with verizon. It's all a possibility. If you credit is truely good, you should be able to bring a copy of your credit report from one of the three credit companies, bring it to the rep, and they will send it to t-mobile with a few other pieces of information and your credit class should be revised.