Contract gone wrong

In 2016 August 28 i ungraded my open contract to top up. In the month of September they send me a bill saying my contract has gone up to close to R9000.00. I called to ask how is it possible as my contract is not open is on top up. I went to the nearest Vodacom shop i was told my contract was not upgraded. I then went back where i did the upgrade only to find out that it was not only my contract but other contracts that has not been processed by Vodacom . In the very same case the lady said i had saved her as she was not aware of that incident. Vodacom then credit noted on +-R7000 of the R9000 plus which i have been paying my contract more than my installment incase there are days i couldn't pay. I have been blacklisted for the remaining amount i have tried several times to get help with no response. I did Facebook, twitter and haven't heard anything form them and they now blocked my account and they want me to pay the outstanding amount whereas i was not on the wrong they did not process contracts and if it was not me the shop would have lost thousands of rands that month because of their recklessness. Now they have handed the matter to the lawyers.