Incorrect Billing

I am on the 10GB Promo for R199 per month. On 03/12/2015 i received my Dec Bill which reflected an amount of R299 i immediately called the call centre to query and was told to call the next day as the system hasnt been updated. On the 04/12/2015 i called and the agent informed me that i was only on the 22nd month of my contract and that she requested the accounts department to correct the bill, i received a reference number ***5 and should receive feedback by 10/12/2015. To date i have received no feedback and each time i call the call centre i am given conflicting information. Today i was told that my contract concluded at the end of November and that at the time of my initial call the \system hadnt updated"the previous agent said it will conclude in Feb 2016. so for 2 years your system hasnt been updated. I was assured that the bill will be corrected and that i can only cancel the contract in Jan 2016 only to be told now that it has already been concluded. How could that have changed in 2 weeks!. """