Paid up letter request hell

I have paid up my account on the 1st of February 2022. I have been struggling to get hold of someone to assist me in getting a paid up letter ad confirmation that the account is closed in order to receive a clearance certificate. Before I paid up the account, I phoned and emailed them to get the settlement balance. Took a long time for a response. Every time I call, the line either gets put on hold or cut off. When I do get to speak to someone, they have no idea of whit it is I need and then usually gets cut off once I say something. Why is it so hard to get service if I have put in the effort from my side to uphold my promise to settle my account.