I just bought a 2001 Pontiac Bonneville and the driver's seat belt has a small problem. It tends to curl in the vertical direction, which makes the sides poke me in the chest in a rather uncomfortable way! Do I need to replace the whole seat belt to fix this problem or is there a way to purchase a straightener or other device to stop the curling?
Seat belts are an important part of your car's safety system. It probably would not be wise to interfere or adjust the seatbelt mechanism by installing an after market device that could affect its performance.
Seatbelt material doesn't ordinarily curl... is it possible that it just needs to be washed to remove some kind of soil that might be stiffening the belt?
Otherwise, I would do what your dealer or authorized Pontiac repair shop recommends. If you are for some reason skeptical of the recommendation from your first diagnosis, you could always get a second opinion from another shop.