MTN taking money off deceased persons bank account.

My son Simon Venter passed away 19 November 2017. Within two weeks of his passing I went to MTN Tzaneen Lifestyle Centre to de-activate his account. To date this contract is still active and MTN are still deducting money off his account, as at 27 March 2018, R4097.57. We are still grieving our son's passing and MTN just do not care. I expect an explanation on why this is happening and a full refund of monies "******" with interest.