MTN continues with their abysmal resolution to their billing errors

3rd post for follow up on the same issue. Please refer to previous complaints on this site. The last post actually got some action from MTN. I got lots of phone calls, lots of apologies and lots of acknowledgements that they had *****ed up and would rectify it by passing a R1k+ credit on my account. WHY THEN IS THE LATEST DEDUCTION FROM MY BANK ACCOUNT R112 MORE THAN MY BASIC ACCOUNT LIMITED AMOUNT WHEN I DID NOT EXCEED ANY OF MY ACCOUNT INCLUDED MONTHLY ALLOWANCES? I can only access half of my invoices and statements online as half of them give errors so I can't see all the activity on my account but my basic knowledge of maths tells me, if my monthly contract amount is R705 and you owe me more than R1k in correction refunds, you shouldn't be taking another R817 from my account!?! I am a professional person with an hourly rate of R1k+ and you have wasted at least 5 productive hours of my time with what I thought was simple matter! What is your strategy here? Tire me out with your adminstrative competance until I give up?