MTN ****gery *******

I cancelled my contact wit mtn in march or april 2019 and went on prepaid. Every month since they have been debiting my account with amounts varying but this month it was R270. For What? Been to MTN store at Mall@reds and they confirmrd my no. Is on prepaid. Dialed 135 7 times and every sigle time their consultant tries to put me through to the "contacts" department the connection jus dies. MTN is *****ing my money every month and there seems to be no way that they resopnd.