MTN *******ly renews contract of deceased person

My mom passed away in early May, I have contacted MTN Via email and also visited the store several times. I requested that the number be put onto prepaid account as the contract was finished end of May. Instead they went an renewed the contract for another 24 months without any consent. I again went to the store at the Glen who made the error and they said they would escalate and rectify. That was almost a month ago. The account has still not been put on prepaid. This is seriously wasting my time, how many times must I request the number be moved to prepaid. Also noting, how can MTN just renew a contract of a deceased person, this cant be legal. I am not resorting to Hellopeter in hopes this can be resolved