Why won't OVO replace my boiler when I have cover?

Called ovo on December 7th 2025 to say my boiler stopped working, they sent someone out a few days later he said there was so much wrong with it, his suggestion was a new boiler also it was dangerous because the flue was broken and birds have a tendency to hid in there for warmth which could cause a fire. Ovo wasn’t happy with this report so wanted a second opinion someone else called out, I then phoned everyday for over 5 days to find out what was happening the engineer didn’t get back to them and they were waiting for the report, in the end I had to say surly he wasn’t reliable and to send someone else out, so now over the last few months I’ve had numerous engineers back and forth each time with a 8am-8pm time slot which is really inconvenient when I work, they change a part it’s working before they leave and then an hour later once they have left it’s not working again. I’ve been told it’s dangerous and high carbon monoxide levels, then I’ve been told it’s fine. They suggested to send an actual baxi engineer but because it was Christmas time they couldn’t send the engineer out. I went on holiday in December only to come home and it had been leaking all over my wooden floor, now I’ve been told exactly what the very first engineer said all along that it can’t be fixed and I need a new boiler, but they won’t give me a new one because it’s over 10 years old, it’s now February 15th I’ve been with out heating throughout the coldest months December, January, February and still no response from them, but they are still quick enough taking my money every month! Even though they know I have no cover!