credit score in jeopardy because of identity!!

i had an account with identity for almost a year and i always paid it on time. it actually boosted my credit score. however i closed it last year during the course of October i think and obviously paid it off before i closed it. usually identity sends me an sms or email as to what my balance is etc etc and the amount payable. i haven't received that sms for months after i closed my account and then a week ago i received an sms saying my account t is badly in arrears and i needed to pay R200 immediately. i then called the head office and spoke to a female consultant whos attitude stank. that however isint my issue . i app**** for credit and i was told my credit score is pathetically low and my account was in arrears. this had me stunned now i have a bad credit record because of identity. i am going to take legal action and i have every right too as i have the proof of payment when the account was closed, the cashier recognizes me and a call recording between myself and the consultant and i distinctly instructed her to close the account and she assured me it was closed.