Vodacom debits every month after contract has been cancelled.

Extremely annoyed with Vodacom. My mother had a contract with Vodacom, when she had financial problems the monthly debit order was changed to my banking details. My mom then passed away, but I continued paying until the contract had run its 24 months. The contract ended this year June. I went into Vodacom The Bridge Port Elizabeth with my moms death certificate. The paperwork was email to Vodacom legal to cancel the contract. I am still being debited every month by Vodacom. I have tried calling numerous times and going into the Vodacom stores - but no joy. How much longer do I allow Vodacom to ***** from me every month. How do I cancel the debit orders going off my account?