Arears

Hi, I opened an account at Lewis 2018. My monthly instalments is R1118. If pay theme R1200 every month and I'm never late. I'm tried applying for car finance but couldn't because of Lewis..They say my Lewis account is in arrears and d I've missed a whole years payments... If tried calling head office trying to find out what problem is and they can't assist me or even try to find out what problem is because according to them I'm missed payments...If have proof of all my payments that is made each month.... If still owed R14 000 at the end of 2018 and after paying R15000 my account is still R12999.How is that even possible? REALLY ****ED OFF AT THE STORE!!!!!!