Please provide calculations of the credit

Hi Mantoa<br> <br> I see there's a credit of about R452.00 in the Aug '15 invoice. May you please provide calulations as to how the credit was derived. I was overbilled since the inception of this new contract by more than half and I see that despite the credit I owe MTN R400 for Aug '15. The past invoices shows that I've been charged for smses despite having more than 200 sms available to use.<br> <br> I would really appreciate it if I can get an explanation of how the 'amount due' as reflecting in the invoices is calculated (given the the fact that I'm on my MTN choice R360.00, with the limit up to R100) as well as how the credit was calculated. Reference number to the previous communication from you is: ***