MTN Billing issues

Since starting my contract with MTN their debit order has never been processed from their side so I always had to do a manual payment on the 3rd or 4th just to make sure they do not cut off my line. Then this month I only processed my manual payment on the 5th of April which is not a problem but on the eighth I received an email saying they will disconnect my line if payment is not processed on that same day I also received an email saying thank you for your payment although they had disconnected my line temporarily. My contract is R403 with nothing to be added however after this accounting error from their side I now received an email stating that I owed R413 something. I tried contacting empty N directly via two different numbers the one didn't work and the other one didn't have suitable options. I need to resolve this problem because they think I owe money wow I have proof from their payment system that I paid on the fifth even though on the eighth they had a problem with my line. It is nearly impossible to reach someone to try and resolve this simple issue simply because they are not processing their debit orders correctly.