Whoever hung up the Courtesy Phone really wasn't being very courteous.
Old Phone + VoIP ATA Adapter + PoE Adapter = I can use my phone again!
My old phone refuses to charge from anything but a car charger, so I had to improvise something in the office
...so this was the solution.
Had a slight reception issue with my Samsung Galaxy and after a couple of moments of research, I decided to repair it... A length of copper wire and a roll of sticky tape later, it works better than before, believe it or not.