Atrocious treatment by MTN

My mum has been trying since July to cancel my dad's current contract with MTN as she it has come to an end and she is retiring next year. I have taken out 2 new contracts with MTN in order for my dad to port his number to one once the cancellation has gone through however due to the atrocious service we have received we have not been able to do this.The call centre called her to offer her a new contract due to the current one ending and she was advised that she had to go in store to do it. My mum went into the store at Midlands Mall in July and was advised she could not do the cancellation instore but had to call to cancel. She tried numerous times and everytime she presses the option to cancel they never answer. She has run out of airtime and just been ignored. She has subsequently been to the store on 4 occasions to get assistance and she keeps getting the run around. For someone who is being a responsible citizen and getting her affairs in order as she will not be about to afford the monthly amount to be given such bad service after being a loyal customer since 2003. Why should she be forced keep the contract when she will not be able to afford it and I have made alternative plans by taking out the new contracts. On her last trip to the mall on Friday 7 October the consultant said she should use my dad's phone(the contract she wants to cancel) to make the call which she attempted today but that did not work either as they cut my mum off after 35mins. We were even advised by one of the consultants when I went to the store with my mum on Saturday 1 October that she also battled to have her contract for a laptop cancelled and they had her on hold for hours. Its really so frustrating to be treated so horribly by MTN all because they want to continue taking money even if we can't afford it. Help in this regard would be greatly appreciated as this cannot continue to go on.