Exchanging Treo 800w for Treo Pro

[yve]

Hello all I'm student winmo user trying to save a buck, If I get a new 800w from fleabay can I bring it back to a local store within 30 days an get the pro ? or this policy only works for new accounts ?
I currently have two SERO accounts with a 1-1/2 in contract and $ 4.00 insurance NOT TEP.

Any ideas ?
Thank you all in advanced.