Cancellation nightmare and Higher Installments without notice

My mother in law called last week to cancel her contract before it goes pro rata, they told her it has to be a 30 day notice and that she should call today (30/12/2019) in order to not be charged in January. She called her today and they told her she will still be charged in January because it is not a 30 day notice from today. With MTN, she has never had a problem like this, you call and you cancel especially if you are contract is finished. Vodacom has also been taking extra money off every month as well, the installment increases every so often. She is still waiting for the consultant to call her back too, because how can she not cancel her contract and still have to pay in January when the CONSULTANT TOLD HER TO CALL BACK TODAY so that it can be CANCELLED. Please cancel the contract!