Contract cancelled but still debiting

what does it take to close a mobile account? my mother has endured pain and suffering due to *********** staff at Germiston Golden walk informing her that the account has been closed but she still receives letter of demands from lawyers and her account is always been debited. This is really unfair to an unemployed lady who gets victimised because she has no power to fight for her rights. May you please close her account and refund what is due to her if there is any.