Cannot cancel contracts with MTN, customer care service broken

I am struggling to cancel my 2 contracts with MTN, which have both expired in March 2023 already. The customer care number of 135 is broken, it puts me in a loop, and no matter which option I choose, it always directs back to the main menu.

It costs me +-R500 every month I cannot cancel the contracts and make them pre-paid. I did go to the Stellenbosch branch, but they directed me towards the 135 customer care number, stating they cannot cancel contracts from a branch.