Anyone with FlexPay from T-Mobile and a Blackberry, please help!

So, I really want to habe teh blackberry data plan for my 8900, but I dont want to be attached to a contract and T-Mobile seems to be my best bet. Can I purchase only the Blackberry data from their FlaxPay and not the minutes plan? If i have the voice call plan I would have to pay $65+ monthly, but if I can only get the BlackBerry data would be $35 or so. Please help!!