***** on account after closing the account

Someone **********ly purchased on my account last year around June 2014. I submitted everything Egdars asked me to submit to prove that I did not make the purchases. Everything was sorted out and the debt was removed from my name and I closed the account thereafter. I recently received a letter stating that my account is in arrears and when I phoned them they confirmed there were purchases made on the account in December that i closed before the purchases in December. I don't have an account with Edgars because I don't want anything to do with Edgars. Busi from ***** department even suggested that i go back to Edgars store. I don't understand why I should waist my time and go to Edgars because they were careless to allow the purchases after the account is closed, worst of all there was ***** case on the account.