I understand you are from UK or Europe so your rights are quite clear and who is responsibleHuh? I bought from my carrier and after 4 months of ownership they won't take it back lol. Nor do they do repairs on site...and nor I expect is there anything wrong with my phone. In-screen fingerprint scanners are new tech and not fully ready for public consumption so far as I'm concerned....
Your first point of contact is the store you purchased it from
If you do not wish to exercise your rights that's fine but bleating about an issue you can't be bothered to fix is just rhetoric
If they cannot help you etc then you have a case to grind else its just self inflicted griping