REFUSAL TO CANCEL CONTRACT AFTER CONTRACT END

I had a contract with VODACOM and when the time came for me to cancel, they refused. I was cancelling my contract with VODACOM because I was going on pension. They stated that they would just reduce the amount I was paying and that I should not cancel the contract. Now the lines have been disconnected and they state that I should pay an amount of around R 5000 that they indicated that I owe.

My plan was that when I go on pension I would have paid up the contract. My last cotract with VODACOM was from Janunary 2020 until January 2022. This contract was cancelled successfully, however the older contract that was opened more than 8 years ago, they refuse to cancel even when I stated my reasons for cancellation. The account numbers of the contract they refuse to cancel are: NA026549-5 and I***-4. I would really like to cancel these contracts since I am now on pension.