Angry customer

Hello..on 28th September 2019 i went to Mr Price In Craddlestone to settle and close my account ..i did all what was required as cashier instructed. My problem started when i went thru my account via my phone app only to find out that i have an outstanding instalment to pay by 30 October 2019.. I was very shocked nd went to my nearby Mr Price store to enquire, and indeed my account was not closed..i was told to pay off that instalment so that they can close my account..i told them i wont pay because its their stuff neglegence they told me i should go back to Craddlestone to sort out my issue.. Bad service indeed Mr Price..somebody ddnt do her job well then customers end up paying ..