Account paidup and closed 5 to 6 years (2015/6)ago in arrears. Now 2022 I must pay

I took out a 2year contract with vodacom in 2013/4 until 2015/6...paidup the account and closed it, now after 5/6 years im harassed by a company named "MBD"...dont know if its collectors or lawyers, im told that my account is in arrears and i must pay. So for the last 5 to 6 years i had not heard anything or had not known about this *** i was under debt review, all my debt and accounts were paidup and closed. It is surprisingly miraculously that this account that i dont know anything about...that was non-existant somehow is going to get me blacklisted or something. I don't have proof that I paid the account and it was closed so I'm taken advantage of.