Cancelation of sim contract

We took a contract thru MTN agency Mobileplus,they promised a sim of 20G R99 per month and was going to keep old number we took it. Delivery happened in October with 2sims and was told of r199 per sim and new numbers. I contacted MTN to cancel they said they only way to cancel this contract is person passed away. We tried the number that called for the contract,doesn't go thru after a while trying to find ways of canceling this we were given an email address to use to cancel, the lady there said they busy investigating and will come back to us,since Nov they still investigating, Dec 1st deduction went off how do they continue deducting if they investigating the cancelation which on the email reiterated that we no longer want any more because we not happy with the service, till now still not canceled. Who can assist with canceling this contract, we no longer interested and want it to stop