You need a PoE Switch. PoE means the ethernet line has power on it. Most switches dont do that because computers don’t need it. Most phones, however, get their power from their signal line so they need it. This is something more than just a gigabit 10/100/1000 ethernet switch so don’t just go buy one from walmart. But that is also less than a managed ethernet switch so don’t go waste your money on one of those. Go to amazon, put in ‘poe switch’ and look for one that has gigabit (or it might say 10/100/1000). ALternately you could get any old cheap gigabit switch and also get a device which inject power into the ethernet line. That is probably the cheaper route. If you search amazon for PoE switch some devices like that will be in the list.
Chances are his phone has a separate power supply, but if not, then yes, he’d have to get a PoE switch. I’d be very surprised if his phone didn’t come with a power supply, though.