Prescribed debt

Hi I had an account with Woolworths ten years ago. Now after all these years I get threatening sms's from NBD to pay my Woolworths debt. I have go no proof of any payments anymore. I phoned Woolworths Financial Services and they informed me that this account was closed and settled. As far as I am concern there is a law that protects you as a consumer. According to the National Credit Act of March 2015 it is ******* to harass people for old debt. I have not proof at all after all these years. The irony of the story is that now after six years I get messages where they threaten me. This is really ridiculous. I have no debt with Woolies anymore and they told me to ignore the messages. Where does Norman Bisset get there information. Even more where did they get my work cellphone number.