Money in arrears while contract was cancelled

Vodacom is claiming money that is not theirs , my mom who is 62yrs old contract came to an end in July on the 1st of august we phoned Vodacom to cancel the contract still end of august they debited the account and had to go to the bank to reverse as it was not authorized we phoned them on the 5th of September and still they did not cancel they said its fine as they had also reversed the airtime they put on the phone just now around the 15th of October I put 1gig Data for her costing R99 and today they have locked her whatsup and she cant send any messages and they have the nerve to say she is in arrears. I just cant understand why if you want to cancel your contract they refuse and I ask for the recordings of the two phone calls they say no because we phoned and did not say anything. all I need now is for them to pay us back our data back and we are not going to pay any cent as we cancelled the contract it is pathetic to want to rob old people and next thing we are moving to another network they must sort it out if they still wat to have clients because I was the one keeping the whole family to be using their network but I am also fed up if they have a problem they must call me on ***- Nonhlanhla