Horrible service rendered by MTN

I am very disappointed with the service, I received from MTN.

I bought home wifi of R280 a Month, MTN has deducted R 485 instead of R 280, their next invoice is written R 746, meaning end of December they will bill me R746.

I have been trying to get hold of them, i have sent emails, no response.

It even worse because their network it not working and it been a 3rd day today.