Poor Service from MTN Call Center and billing department

Took out an cellphone contract with MTN (very happy with it), then I took out an data contract that was also okay until I upgrade the data contract to a better one. The router did not work properly and I return the router and my contract was cancelled. End of September 2020 MTN deducted an amount of R2051.76 from my bank account and after several calls and reference numbers it was not solved. On the 08 October I decided to take out another data deal from MNT for R299 per month. Big was my surprise when I received my account today 14 October 2020 for an amount of R3872.72 that will be deducted from my account on the 1st November 2020. After calling MNT again i had to sent the contract to them as they need to sent it to billing to sort out. This is not on i will not pay tht amount