Unable to get confirmation account is closed

I am battling to get a letter confirming account is paid and closed since the 07th August 2020. Phoned last week Wednesday, 19th August 2020 requesting for this letter and was told would have it within 48 hours. Phoned again late Friday afternoon to be told that, that division was closed. They acknowledge account is paid in full and no one can advice as to who can assist with supplying letter as requested by emails which the also acknowledge they can see. Was promised on Friday that she will escalate my request first thing Monday, 24th August 2020 and will send proof of letter as requested. I mentioned that this letter is needed urgently as I need to send it to the bank and would appreciate her help.

Phoned on Monday, 24th August 2020 mid morning to be told the same thing and now I am going to wait 5 days before I get the letter.

I would appreciate if someone can assist me as I need this letter for the bank otherwise we are going to lose our bond and loose financially.