Useless boiler & customer service

I got the Heatline Bolier installed about 2 years back after an engineer recommended it to me. The boiler was installed and serviced every year. Since the installation date, every 2 - 4 weeks the time switch will automatically move from the ON position to the Timer position. I tried calling heatline a few times but as the waiting time was too long, i never made it through to report the issue until last week.
I reported the issue to the agent on the phone, he read a statement that if the issue is not related to the boiler they will charge me. I asked the agent that the timer is part of the boiler, so will i be charged? He instantly said No as it is part of the boiler so it is covered as long as the boiler is covered.
An engineer came down and first thing he started inspecting the boiler and checking the flue. 2 minutes later he said he will not touch the boiler as there is a different make of flue installed to it, and the boiler is as High Risk ? I asked how should the flue be installed to be properly installed, and he replied the boiler is at high risk so he need to turn it off. I asked the same question again and this time he gave a totally unrelated reply. I said this is not my question, and showing a sarcastic and stupid smile he said do i have your permission to turn off the boiler ? His behaviour reminded me the corrupted people who wants you to give them money to go ahead with your work. It was very clear to me he doesn't know how the flue should be installed, they just make up issues so that we buy their product. He still never said how to install it, the closer answer i got from him was to check in the manual how it should be installed.
I called my gas engineer and he confirmed me the same thing, that they bring up all kind of issue just to force us buying their product.
So for a boiler that is not even 2 years old, an issue that came up since day one, brainless engineers, I think this boiler, and their customer services, are a full disaster. The reason why the boiler is sold on the cheap, is to be able to dig money out of customers after the installation.