Debit order payments

Last month MTN due to no fault of mine did not deduct their debit order off my account which is their responsibility & blocked my account, I went to PE branch to sort it out. Only to be told I had insufficient funds in my account & that is why debit order was returned. Had to go to the bank to get a statement to prove to them the month of May R611.59 was deducted on the 05/06/15. I then made and eft payment for the month of June of R686.21 so that I was up to date &then confirmed with Carol at PE branch that all amounts reflected as paid. Yesterday I got an SMS stating that R1 240.71 will be deducted from my account FOR WHAT? I again had to contact the call center only to be told they can't see why this amount is deducted. How is that possible? This morning 04/05/15 I went to print my account on MTN's website & see that the amount for July is only R606.32. I again contacted PE branch & spoke to Carol whom has said that she also cant see why this amount of R1240.71 was deducted & that MTN has charged me R11.79 for debit order returned which was as I said not my fault but MTN's but still there is a difference which was deducted *******ly from my account & dont know why or for what.