Over Billed - Case Number ***4

I upgraded my contract last month only to be invoiced a Device Obligation of R 2,277.00 for a SmartInternet Top-Up 500MB + Modem. The total cost should have been R139 per month with a little more being added this month for ProRata. This is clearly an error and the Accounts has taken more than 72 workings hours to correct my invoice. The online chat can only tell me that accounts is still attending to it. If this is not sorted before my next debit order goes off, I will be forced to reverse the payment and I do not want it to come to this and tarnish my reputation as a good payer. I have been a loyal customer for many years and I would hate for something like this to force me to move over to another network. I need some answers and action urgently...