Accumulating fees on closed account

I keep getting calls and messages of an account that was closed 4/5 years ago saying I’m owing. I’ve emailed Edgars complaining about this and also received a call from RCS. I’ve explained my case, apparently late last year a new policy was implemented, my question is how does that policy apply to someone with a closed account? I haven’t bought from the shop in years yet I’m said to be owing… This is frustrating Edgars needs to sort this out!