Presumably your copper pair 'line' was already installed, so you don't live in a new build property, but a fibre was provided as an 'overlay' alongside the previous copper service.
It may be possible to cease the copper pair line (and phone service) and then have your phone service over FVA ,or not have a phone service at all. but you will not save any money, the line rental then becomes a rental of the fibre rather than the copper pair......and if you elect to cease copper pair phone service and not have a phone service over fibre voice access , then you still need to rent the medium that the broadband is delivered over, the fibre optic cable....just saying you don't want to use a landline phone shouldn't save you any money, because you are still renting a line , copper or fibre optic , it's line rental , not phone line rental, after all , if the fibre optic line developed a fault or was damaged and your broadband stopped working because of that, you would expect it to be fixed, if you didn't pay rental, why would the owner of the fibre cable bother to fix it if you were not paying to use it ? , in fact at the moment you are getting a cracking deal, because you have copper line and fibre 'line' but are paying the same rental as those who only have a copper line,perhaps you should actually be paying more , not less
