go to
http://www.blackberryforums.com/gene...ax-memory.html to try and free up some memory. there is a program out that cleans up alot too. i think its called maxmem or something like that. just make sure you back up before using that program.
if that still doesnt work, try deleting your service books from OPTIONS>ADVANCED>SERVICE BOOKS.
after they are all deleted, go to OPTIONS>ADVANCED>HRT and hit menu and then register.
try texting after you complete these steps. if it still doesnt work, then hit up tmobile via 611 and complain =P