Messed up account

I have a contract that was originally generated in December 2014. I sent the sms to see when it is due for an upgrade on this specific number ********** 775 and my sms response was it is due 21/09/2018. We decided to wait before we upgrade as we still have time until December to do the upgrade. My invoice has increased in October for this specific number and I waited to see weather it would change on the next invoice and now it is more than R1000 once again. I went to two Vodacom Stores and was told that my upgrade date shows in June and the contract has ended and that is why I am paying more but the consultant at Heidelberg mall assisted me by phoning from her side after which she explained and they realised there is a problem with this specific line but the call was unfortunately cut. She told my husband to call again as there is a problem and he did call on 12/11/2018 and was told that it would be escalated and he would receive a call back within 24 hours to get the issue sorted. Today is 14/11/2018 and he still didn't get any call back so we don't understand how we are suppose to get this issue sorted. We want them to fix the problem and would like an amended invoice for payment on 01/12/2018 which includes a credit note for the previous payment that was deducted from my account on 01/11/2018.