Hi there

Our fibre ONT is going to be installed in our garage, from the modem I had planned to run a cat6 cable up to a switch in the roof space and from there have some ethernet ports installed in a few places where AV equipment might be and to a wireless access point. I had asked to keep our existing phone wiring when I bought the fibre. 

I discovered that there is already a cat5e cable that carries our phone line running from the garage, up into the roof space and then down to where our existing phone is, I think it daisy chains to another phone point as a second cable comes back up to the roof space again and off across the ceiling. Our phone points are rj45 connections and we use an adapter to plug a standard phone in. 

Given that there is already a network cable that is probably good enough for home use already running where I need it to go, could I somehow break or split the cable at both the garage and the roof ends so that it can carry the data from the modem as well as the phone from the garage to a switch in the roof space, and connect the existing wall points plus any new ones to the switch and have the phone still work? 

The garage is not directly connected to the roof space as we are on more than one level, but I don't think that it would be too hard to run a new dedicated cable though following the existing cables if that was simpler. 

Apologies if the above is fairly nonsensical, as you can probably tell I'm not technically minded. 

Thanks