UNABLE TO CANCEL AN MTN CONTRACT

I have been trying to cancel an MTN contract with no luck, when I go to the store to cancel, they tell me that I need to call 135, everytime I call 135 I am not able to get through to a Service consultant to cancel as the voice prompts always say they are not available and that I should call later, this has been the case since 2022 :( Every month I accumulate money for a contract I have been trying to cancel since forever, which I could have used for something else.