Frustrated by MTN

I am sooo annoyed

I have a MTN data contract sim card with MTN. I was under the impression that my sim card was no longer working abs I stopp6payong and using it since I think Feb/March 2023. I then received a call around October that my account has been handed over and I had a balance of about R2100. I went to store arond the 20th of October at wonderpark MTN store and asked my balance. I paid my total balance of R2100 and I was under the impression that I am done paying. I started receiving calls that I still owe MTN, but when I went to store I was told that my account is up to date. Today I received another call that I owe about R400 and a couple of rands and I was told that the MTN branch does not have full information as compared to the head office. This is frustrating, can MTN resort their problems please, I can't pay over and over again.