Postpaid Contract Cancellation

I have been trying to cancel my postpaid sim contract.

Had signed the contract back in September 2016, while buying a Samsung phone. The contract has been renewing itself ever since 2018.

I have given the notice of termination multiple times since, but still could not end up successfully canceling the contract because I never happen to get hold of anyone to speak to when calling the suggested number to 'confirm ' the termination.

I would very much appreciate if someone here can assist me in canceling the contract.