Very poor human relations

I had a month to month contract with tracker which I cancelled in January 2022 because my car was in an accident and it was written off. Tracker kept on billing me and handed my account to MCS. The rudest lady from MCS started calling me and harassing me for payment. I then called tracker and they credited my account with the full outstanding balance. I tried to explain to the lady at MCS that my account was closed and fully credited. She didn't want to hear anything about it even after I explained her to contact tracker. She said she wont listen to my explanation and she will not contact them. I cannot recall her name but I'm sure they should have a recording.