FRUSTRATED!!! Slow to Close account

I am extremely disappointed in the handling of my application for closure of my account. On 28 August 2019, I have paid up my Builders Card account with the aim of closing it. I have contacted Builders numerous times after this confirming that payment has been received and they are in the process of closing it. There was an issue where my account was overpaid and I had to be refunded the excess but that has since been resolved. I have since 28 August been requesting a paid up letter but have still not recieved anything. Today is the 12 September 2019, 11 Business days since I made the initial request and still have not recieved it.

All I require is a paid up letter confirming I have paid my account in full and that it is in the process of closing it. Yesterday I called again and was promised to receive this letter by the end of business yesterday but no such luck.

This is so frustrating as I need this letter urgently.