account paid up - REF ***

I'm writing this on behalf of my husband. This account was paid up to date in March 2020 and we are still receiving messages of unpaid amounts. We keep telling them that this account is paid up, sent them the POP and still sending emails and calls. I need someone to urgently look into this as this is very bad service and we are battling for them, to close this account. We haven't bought on this account either.