Jet is unprofessional and ****s customers

Jet is is franstrating my mother by calling her on a daily basis telling her that she owes them after she paid up her account last year (2020) in September and later called their call center to close the account as the jet in Tzaneng mall said they don't close accounts in store. She spoke to a man called Madoda and a lady called Cindy and they both promised that the account will be closed. Now she is getting calls that her account owes over R2000, when she asks what the money is for because she never bought anything after paying up the account she's told is for a policy that she never consent to and jet club. What must one do get a jet account closed?? Why is their systems not in place