he has a problem with his phone out there,
First, we need to hear from you as the type of problem he claims to be having.
Is it one or more of these? NDT, CH, CBH, CBDT, GWN, BDR, BRCM, NSY, HOOL, GCO ?
Have you tried swapping his phone with a known working one?
Have you taken his phone back to the main building and plugged it into a known working jack?
Have you tried using a different pair in the cable?
Have you tested the pair with a vom for metallic faults?
Have you tried temporarily by-passing the protection at one end? at both ends?