Can you provide any further information? Make and model of router and make & model of phone for example. Pictures of the socket into which you are plugging the phone and / or the back of the router showing the ports would be helpful.
Did you have an existing landline number ported to youfibre? If so, did they confirm that the port was completed? Are you reusing an existing phone or did you get a new VoIP phone? When you say you cannot access the router, do you mean you haven't got the credentials for it? Very often the credentials are given on the router itself (unique password for every device). If the wifi is working then the router is working - I assume you can use wifi to access the internet, i.e. outside your local wifi network.