Settled Discovery credit card not updated with ITC

I settled my Discovery credit card in December 2014. An account closure letter was then emailed to me. Since then however, my records with ITC and Experian have not been updated - and it is still reflecting the full outstanding balance as an installment, which is greatly affecting my profile and affordability calculations. I've emailed the closure letter to Discovery Card requesting they liaise with ITC to resolve this ASAP - still no response. Please can someone assist me urgently?