COTTON ON ACCOUNT that isn't even mine, yet they continue to harass me!

Daly Credit Coroporation has been harrassing me for a Cotton On Account that isn't even in my ID number. I have told them it's not me, not my account, not my ID number yet they continue to harrass me every single week via sms, phone call and email. I apparently have to go to a police station to do an affidavit that it's not me, send 10 signature samples and complete a dispute form at a Cotton On Store... Now please tell me why I should do this if it's not even my ID number? I have rep**** and told them to get the correct details from RCS because it's the wrong details for the ID number that has been given to me, but I have been saying this for 3 months now... The harassment needs to stop!