Non-cancellation of a deceased's contract

Pathetic!! Since March 2019 I've been trying to cancel my mom's contract (who had passed away). Having send the relevant death certificate, her ID, a copy of the Power of Attorney and the last mentioned's ID to *** (March, April, May, June) as advised by the call centre agent(s), the contract is still active. Having received the read receipts (March, April, May, June) from '***' I am rather surprised that payments are still taken for this contract. Eventually I had to go myself to Vodaworld, 13 June to have this sorted. The agent at the time promised that this will be sorted and apologised and said that this should never have taken this long. Surprisingly, nothing was done since then and I again went to Vodaworld 20 June 2019 hoping that this will be sorted and finalised once and for all. To my surprise, I got the same response. I was requested to send the documents AGAIN (having done this now 4 times), I refused! The agent said he can't help me if I don't send the documents- really!!!! I have send it now 4 times (with proof that it was received and read). The agent ('Lele') that initially assisted me at Vodaworld apparently also mailed the documents however, I have not received any reference as she indicated at the time, having promised that she will cc me on the email that she had send directly to the relevant supervisor. The agent also promised a call back from her supervisor (Phumzile). I got the same response today however, I have received no call back since 13 June- I'm still waiting. The contract is still active, unacceptable Vodacom!!!!!!