Cat5 wiring shared for network & phone?

[guitarbot@xxxxxxxxx]

Hi,
I paid an electrician to wire cat 5 to 5 rooms in my new house.  He was
told that they were for My computers & they would all go to 1 room with
a hub.  He wired it, but didn't run phone lines to some rooms.  He
isn't coming back (it's a long story).  Can I use 1 cat 5 cable for the
computer network & a phone line?  ie: Are any pairs on a cat 5 cable
not used?
Thanks,