We have a group of phones in a certain department, where everyday the calls are delayed, have static or drop the calls. We have SIP trunking but our provider points all fingers to our PBX. How do I go about troubleshooting this and why is it the specific group of phones only?! My only possible guess is that around the time this issue started happening was around the time they built a new room below this department. This room is somewhat directly beneath this department and they installed two LED linear highbays. Should I attempt the route of trying to run new cable to this 2ND floor department? I do believe that the homerun cables in the ceiling might not be STP, which is why this issue is happening. Whats your opinion, should I take the physical or technical approach first, considering I don't know how to wireshark the IP phones.