Billing Allocation Error/ Bad Service

I have never received such bad service from any provider before! Customer Service is suppose to be just that but MTN clearly does not provide any assistance. I have had my line suspended 3 times in the last 2 days. Calling and explaining that R2300 was paid but MTN allocated this amount to current balance and not 60 or 30 days is useless because all I get told is that I am in arrears, which I am clearly not. I have sent my statements proving this but still no feedback and when calling the Call Centre you get treated like you have done something wrong. Not the best way to treat your customers! Please can someone sort out my account because if my line gets suspended again I am definitely cancelling my contract and moving elsewhere!