Still being billed for account closed over 1yr ago

I closed my Hub account in January '15 at the Phoenix branch. The person processing my request confirmed that my account was fully paid up and that it is confirmed as now closed. The account has been inactive since. Over a year later, I now received a statement dated 05 March 2016 with a balance of R92.76 owing. I called the customer service centre to complain this morning and after spending more than 20min explaining the situation, the response from the operator was that they could not help me and that I just need to pay as it is my word against the Phoenix store that the account was indeed closed! They also said that I should go back to the Phoenix store to dispute further. What kind of administration systems do these people have? Its a joke to say the least! Why is there even a customer service centre when they just refer you back to the store where you received poor service to begin with? I would appreciate fairness and ethical behaviour when dealing with a retailer of this magnitude. Appalled by this kind of service and my expectation is that you resolve urgently as this problem is clearly due to someone within your organisation who has not done their job!