Vodacom not cancelling contract

On 10 November 2018 I received a cancelation of contract from Vodacom that I requested. On 13 November 2018 I sent the cancelation document together with proof of payment to ********** for Vodacom to cancel my contract. To date the contract has not been cancelled. I made 3 follow up calls to the contracts department on which they promised to cancel the contract. Clearly that has not been done!!