Vodacom contract

I called Vodacom yesterday to ask for my balance as I wanted to settle it and close it same time. When I called in the morning, they said it owed an amount of R475. I payed the amount the very same afternoon. I made a call again this morning to vodacom to check if the balance was reflecting on their system...the lady said yes and that I can now call retention and cancellation section- which I did. When I called they said I must call after 4 hours. I waited another 4 hours then called again. When I called, the consultant told me it still hasn't reflected and that on his system theres a balance of 600+. My contact was for a period of 24 months, yet they extend our contracts to more than the agreed term. Their email for retention never goes through. It bounces every time but they dont forget to debit my account. And why can't they tell me the exact amount instead of giving me a balance of 475 then 600?? Money doesn't grow on trees.