Wait, if BlackBerry Messenger works, all you need to do is follow the instructions Stickied at the top of this forum for using a Storm on ATT or Tmobile... same instructions work for the Tour. I assume your email works ok too?
If all that is true, your device is registered on Tmo and removing any registration from Sprint is no longer needed.
Here: Unlocked Storm on AT&T or T-Mobile
So the key here is that BlackBerry Messenger, email, PIN messaging etc., works now.