You could make your case more compelling, perhaps, by demonstrating to the court the sound that your seat belt alarm makes and having one of the people from your phone conference testify that the alarm wasn't sounding during the call. That would seem like quite a bit of work, as well as inconvenience for your witness, for a seat belt ticket and it wouldn't guarantee success; but straight "he said, she said" contests are usually resolved in favor of the officer.

