@SammyWoo:
@JKnott:
It's obvious someone doesn't know what they're doing.
Nah, I wager is one of those just doing enough the get by. Contractor didn't want the hassle to run a new cable, so use old one with 1/2 pairs. this puppy is gonna come up again at upgrade time, hope the cable is outside of DMARC (ISP responsibility) 'cuz if it's inside, customer's expense to fix/upgrade.
The problem is these days Internet connections often exceed 100 Mb. Mine now offers up to 1 Gb. If the contractor takes pairs for phones, then that connection will never exceed 100 Mb, even though you may be paying for more. It's just a bad idea. Incidentally, other than for Gb, there is not a technical problem with having phone and Ethernet in the same cable. The original spec for what became 10baseT (StarLAN) was designed to work over 3 pair CAT3 cable, with one pair used for the phone and 2 pairs for Ethernet. However, these days it is considered bad practice.
I have also seen contractors do lousy work. One for my sister's cable TV company stapled the black coax right down the middle of the living room wall! On the other hand, when I had a cable modem installed, about 20 years ago, the first guy that showed up wanted to run the coax along the baseboards & around doors etc.. I refused. They then sent 2 men, who took 3 hours to fish the cable from one end of my condo to the other. I also had them pull in a couple of runs of CAT5, so I could have network connections at the other end of my unit. They did a very nice, neat job!