Bad Credit Record thanks to MTN

Last December I received a statement from MTN that said my debit order will go off on the 3rd of January 2015 and not as usual on the 20th as arranged. So on the 20th my DO didn't go of and also not on the 3rd of Jan as the statement said. On the 20th of January it went of twice and on top of that I had to pay interest on it. So I called MTN on 808 and they couldn't give me an answer as to why this happened they only ask me didn't I change the date which I didn't. I also the guy won't this affect my credit record and he said no after 3 month's of non payment they give you over. So now I received a statement AGAIN that said the amount will go off on the 3rd of Feb... and when I called MTN SA to ask what's going on the lady kept on saying that they don't debit on the 3rd and that my do bounced on the 20th of last month that's why my stuff didn't go off which I know isn't the truth, she kept on telling me what she thinks and even when I told her I understand what she means but I have the mms statement saying something else and that she should let me speak she kept on speaking until I ended our call - STILL WITH NO ANSWER!!!