Fibre can’t access most websites!

[#1]

I joined plusnet at the start of December. I have had no fibre broadband since joining. When I try to access websites on a select few work with the rest showing ERR_CONNECTION_RESET. Google, plusnet(partially) and sometimes YouTube work but no apps or programmes can connect, nor other websites. On top of this only 1 or 2 devices can reliably connect to the router, iPhones seem to be able to tell the cant access websites through the router and so disconnect from it rapidly.

I am about to hit one months worth of service which I have paid for and haven’t received, on top of paying over £90 so far on extra data for my phone as I work from home and no internet is not acceptable. Additionally it took 2 attempts to get an engineer out initially to solve a line/socket fault, as the first was a no show with both appointments being over a week after I called, and have yet to have any meaningful support or help with.

My router says it is connected and plusnet say there are no line issues, are there any suggestions here or help I can receive?

Also is there a way in which I can submit a complaint or look to recoup any funds lost due to these errors as I am reluctant to continue paying for a service I don’t recieve.

Any help would be appreciated

[#2]

You don't say what Router you're using, but if a PN Hub One, try switching off the 2.4ghz band- see if that helps.
The higher band is much less busy so will suffer less interference from other wifi users; I'm assuming you're using wifi primarily.
You can't change DNS setting on a Hub One, but you can on your laptop etc; use Google's to see if that assists:
8.8.8.8
8.8.4.4
Post back on outcome.

[#3]

Check that your DNS client service is started too.