I wanted to post about sarcasm post, but since that is already done...
Anyway I would recommend in least checking logs if there is unusual stuff like forwards to certain address. Or in least get a blackberry expert to check it out. If you have evidence, do as other people suggest here in respect of stalker/abusers.
If not, I would recommend in least hard wipe-out by jl-cmder as others suggested, and after installation, lock it with a strong password.
I would recommend re-installing blackberry OS on your computer if any OS was already installed, on off chance that it was modified there. I doubt it was, but it won't hurt.
"There is no reason anyone would want a computer in their home."
- Ken Olson, 1977
( And we now wear them! Blackberries are computers too! )