Billing Error

I recently renewed my contract about 4 - 5 months ago and I had an amount outstanding from my previous handset which was supposed to be settled within 3 months, when I wanted to go and pay my account I saw that I am still being billed for my old handset plus my new one, the guy at Clearwater mall lodged a query for me for them to check my account and correct my bill this was 3 weeks ago, to date no one came back to me and when I try to phone the number provided there is either no answer or it just doesn't go through. I got a voice call from Vodacom asking about a payment arrangement to which I said the 15th (hoping my bill will be sorted out by then) tomorrow my payment is due with no answer from Vodacom as yet I refuse to pay for 2 handsets while I was assured that the old 1 will end in 3 months time and I bet Vodacom will cut my lines tomorrow if I don't make any payment but the fault is on their side one always have to beg and plead them for an answer regarding any issue you have