Paid up letters withheld

I requested my settlement letter in October and paid in October 2021. I have been requesting paid up letters since October and I am being sent from pillar to post. Latest today is that I still owe them which is so ***** as I have paid the full settlement amount within the specified time. Appalling and so frustrating that it can take so long to get letters other service providers produce in minutes. Not to mention the amount of time and airtime I have wasted on the call center with so many different agents promising to escalate the matter but still no letters.