Still failing to deliver

I made a complaint 2 weeks ago and Discovery pretended here on Hello Peter that they had sorted it out. Long story short, after sending me the WRONG letter, I decided to start all over and talk to someone. After 10 minutes on the phone, they discovered that DISCOVERY made a mistake and promised to sort it out. My niece and I were asked to send my proof of banking which I did. I was told the letter would be sent within 3 days, it’s been over a week now. No communication, nothing. Now I’ve received a demand for my tax to be sorted out. I’m non compliant with my tax affairs because Discovery won’t send me a simple letter confirming that I paid premiums for my niece. What should I do now? Get lawyers involved? Report you to the insurance ombudsman? Coz after this complaint, if nothing is done I’m definitely going to take more drastic measures