My car (Ford Galaxy 3) has this unacceptable bell tone when you don’t fasten your seat belt immediately. It even rings when parking in or when driving slow. After looking for a solution I found the following algorithm (it’s no joke, it really works):
- turn car key to position II,
- turn on headlights,
- fasten seat belt nine times (sic!),
- turn off headlights,
- cut off ignition.
No disturbing tones anymore. 
Just apply above algorithm once more to turn ring tones on again.
Hahahaha, this is great. I just hope this didn’t turn the airbags off as well.
Well it could be dangerous to test the airbags …