Bill me for a mistake done by them

In January 2015 I went to MTN in East gate mall for my cellphone upgrade, i requested that i still be kept on top up and agreed that i will be paying R299 per month for my contract. A month later i noticed that i never run out of airtime, i though its because i buy a lot of airtime, i then chose to contact 808, the consultant i spoke to told me that my bill was already running at about R1200 and that my line was not set as top up as i had requested, i then asked him to correct that mistake and also made him aware that i wont be paying for a mistake made by MTN shop.<br> <br> End March MTN debited about R1300 from my account (my monthly subscription + the airtime), i reversed the transaction, last night they sent an sms saying they will debit R1581.97 (which i will also reverse) month end... For hours now i have been calling 808 with no success, thus this...<br> <br> I will only pay R299 pm as per agreement, not for mistakes done by your people.