MTN - charging you for their mistakes

MTN sold me a business contract without checking things their side! They have now loaded me onto a normal contract but have added packages to ensure that I receive the benefits I was sold, a discount was app**** to ensure that I get billed the correct amount as stated by my contract.

This discount seems to fall away every few months and I have to run around to get a credit refund. My phone has now been suspended since Tuesday even though I pay my account every month. I was told I need to pay the R2169 (that I was INCORRECTLY billed) to get my phone connected again and I will be reimbursed!

Why do I have to pay for their error? Besides in The beginning of the year I paid extra on my account so it doesn't get suspended and I have never been refunded

All they do is comment on Hello Peter that I will be assisted but nothing ever gets done