Please reverse the overcharging

I called MTN during 2015 Easter weekend after noticing that I was billed R1300 which could not add up on my side. The call centre consultant then explained that someone had deposited R500 in my account and upon noticing that it was reversed but then it was reversed twice by mistake which led to my account being over by R500. I have called more than 5 times since then and was not resolved until new debit order went through on the 25th. I called today and the consultant could not even figure out what the issue is since this is such an old issue. Please pay R500 in my FNB account. I have previously given one of your call centre agents my banking details. This has been hanging for over a month. What makes it worse is the fact that your call centre is inbound so I am the one who always have to call. I am tired now and just want my money back please. I need to use it.