Month to Month of trash

I took a month to month home wifi on the 3rd of October, paid upfront, prorata included. This morning I get debited almost triple the amount that I'm required to pay monthly, calling MTN I'm beig told the huge amount is inclusive of an upfront fee and prorata, but this I already paid on the 3rd of October. In addition to this I canceled this contract om the 31st of October but MTN says they have mo record of that on their side, no record of me paying anything on the 3rd of October and ultimately my call got disconnected. I'm appalled , MTN you are *****sters.