The worst service over a bad letter

I have paid up my account on the 6 Feb 2023. I request a paid up letter from this company. It is the 16th I called again now they telling me to call back in 10 working days. For a blady letter really I request to speak to the manager of the call centre and he is on a call . This is the worst service I got from them ever. But when you owe them they want to call you 1000 times . This is the worst service I am going to change my bank account also now because of this services