MTN is robbing me

After sending NUMBEROUS emails and messages on Facebook (which they ignore) MTN is still telling me I owe them money. I sent them my bank statement in PDF form. I even sent screenshots of the emails I got when I made payment through the MTN app. And all they tell me is they received one payment but not the other and I still owe them. And they end it at that. MY BANK STATEMENT CLEARLY SHOWS THE TWO PAYMENTS I MADE AND YET THEY STILL TELL ME I OWE THEM CAUSE THEY NEVER GOT THE SECOND PAYMENT??? And the MTN APP is even worse cause it shows I have four months outstanding which is absolute nonsense.

The one lady I spoke to via email told me my account is upto date AND that I have credit which will go towards my May Bill, but now MTN tells me I owe them and even though they have all my proof of payement they requested they still say no I owe them cause they never got it. Who’s fault is that?? And why did the first lady I speak to tell me my account is upto date AND that I have credit because I paid to much???