Struggle to Cancel Contract

I Have been trying to cancel my 1 data contract with Vodacom since 27 November 2020. I have phoned multiple times the cancellation department. Every time the consultant tells me the contract is not cancelled they will cancel it for me! But nothing happens. Meanwhile sine my contract ended November and it was on a special rate, I am now paying double the amount because the special price does not apply after the end of contract. I have asked to speak to a manager and the consultant said he will escalate the matter! It has been a week and no one phoned me!!! This is unacceptable!