Inconsistent billing due to incorrect capturing of dates

I took a voice contract with vodacom then later a data contract. When time to upgrade came I queried when my data contract would end for I couldn't afford to upgrade both and was told it ends next year March so I had to stick it out. Only when my decembybill came it was a shock and I called vodacom to query that and was told my contract ended 20 November so I opted to cancel only for the cancelation department to tell me I can't because the contract ends in March. I have tried to sort this out for 2 weeks to no fruitful results, I keep getting sent back and forth. I am forced to stick it out with a contract that i can not afford to pay for as they have forfeited my discount. How can a contract ends in November so it forfeita a discount but ends in March so I can't cancell. I feel ****** and forced to pay a huge bill that I can not afford. even now I'll still be forced to pay that bill for December and January because I have to give 20 days notice for a contract to be cancelled while they're not fixing the issue with the inconsistent contract dates and I'm being told I'd have to wait until next week Wednesday which will be too late for the contract to be cancelled. I am also being forced to pay for he mistake that was done by hem on their side because if the dates were correctly captured I could've cancelled the contract last month but I was told it ends next year so I couldn't cancell. I feel ****** and exploited that I have to keep he contract and pay huge bills while it is their mistake. I just want the contract cancelled and he billing fixed because it's not my problem that they captured inconsistent dates which hindered me from cancelling the contract in time.

Dates were fixed but contract wasn't cancelled. I