18 year old Edgards account

I paid my account up in full at the edgars store in The Glen shopping centre almost 15 years ago. The day i went to make the last payment the lady confirmed all payments has been made. Now im getting daily calls from Norman & Bissett, SSDA, RL Daly, Creditworx over this account. This account is so damn old now all of a sudden I owe them a lousy amount. How can you be contacted for an account thats like over 15 - 18years old which payments were in branch.. If this is not resolved i am going to lodge a complaint with the ombudsman.