Can you be responsible for anything from a divorce that is not in writing(black and white)?

My divorce was final last year and I have done everything that has been asked of me that was written in the decree. The decree says I have to pay the car payment till its paid for but nothing about the insurance or maintenance. So I told her in advance that I was not paying for that any more. I took my name off the policy and created a new policy to insure my son and I while he is at school. She thinks that I have to keep paying the insurance also. I haven't talked to an attorney but I'm changing it anyway.