noob question: Upgrading a phone over the T-Mobile.com or in T-Mobile store

I was wondering if anyone has known if the T-Mobile Retailer charges more or less then the online T-Mobile site? I was planning to get a Blackberry Curve. Also if you walk into the retailer, will they still let you buy the phone w/o a BB data plan? (I'll most likely get the data plan if I live off campus in the future)

They charge you almost the same . I think you can get sometimes free shipping ,but I ended getting my Pearlie Baby 8120 at the store because I wanted to see it and I wanted for them to answer my questions.