Charge more that the invoice

I receipt my monthly account for the amount of R384 but my original contract was for R350 per month. This morning MTN debited my account for R465 which is R81 more than my email account. I emailed accounts but you will wait forever. I also sent a tweet but those operators cut an paste answer without investigating. I've reverse my debit order as I am sick of this buck passing. Cannot wait to walk away forever.