Pay back the money

Dear Sir/Madam I have extensively complained about MTN and their treatment of my case regarding banks debits that do not make sense. I have been debited twice by MTN, when in actual fact I have been up to date with my payments. My signed agreement with MTN was that they would debit their signed and agreed upon installment by the 15th of every month, however they have been debiting their amount on the 25th of ever month. As anyone would ask, how does MTN have the right to debit on a date that was never agreed upon? In efforts to try and solve the issue as I am now left with outstanding bank charges, I have been disappointed by MTN for not being much a help. This is my money and my petrol that I am spending with no positive results. To give a clearer view of the events that have taken place, I will disclose the following. In April of 2016, MTN debited an amount of R518 (which is not the agreed upon amount) and then in a matter of five days they debited again an amount of R510 (which is the agreed upon amount). They are now stating that everything has been rectified and my account is up to date which is all good and well except for the part where I have not been reimbursed by MTN the amount that they were not supposed to debit in the first place. Above that I have an outstanding bank charge of R115 which is the result of MTN debiting an amount R1018 which that they were not supposed to debit in any case. They were only supposed to debit an amount of R510. My credit profile is suffering unfairly at the hands of MTN, the least they could is fulfill my request and pay me back my money that they were never entitled to. Also, considering the amount of grief that MTN has put me through, it is only just that they provide me with an explanation as to who is given the authority to change the date of debit which was signed and agreed upon without informing me of such nor my consent. ***