Incorrect Billing

I contacted the call centre, as I am being billed the incorrect amount for my MTN Sky Package. I was with Nashua Mobile, and was being billed R1499. My line was transferred to MTN and initially I was being billed the correct amount from MTN but suddenly my monthly amount has increased to R1799. I received the following reference number: *** and was told it would take 2 days to resolve. I have still not heard back from MTN, and each time I call the call centre, I hold for 30 minutes. This is unacceptable and I need it resolved urgently. Failing which, please terminate my contract and allow me to port my number to Vodacom.