i would call them and have them check provision on your account.
it depends what plan you would like if you surf a lot i suggest to get a unlimited web for dumb phones mine is 9.99 but that grandfathered or whatever you call it
the easiest way to do it is log in to your account and change your phone to samsung t879 i believe its the brown one and add unlimited web for dumbphones and use setting internet2.voicestream.com

you will find it in settings interent connections then click connections and you should have wifi if it is setup and tmobile connections if it is setup mine is names tmobile internet if not click on new and set it up aps internet2.voicestream.com user name blank and password balnk click next and advanced leave proxy unchecked and ip on auto retrieve