It cannot be a "Plain Old Telephone Service" (or analog) issue, because it is working with "VoIP"-- and it's digital since the audio enter at the computer.
Maybe is an "IP conflict / IP duplication", and the VoIP packets go to both IP addresses. IP duplication can be caused by some type of "monitoring/spy" at their (or your) computer, and a dynamic IP address. it's not…
It cannot be a "Plain Old Telephone Service" (or analog) issue, because it is working with "VoIP"-- and it's digital since the audio enter at the computer.
Maybe is an "IP conflict / IP duplication", and the VoIP packets go to both IP addresses. IP duplication can be caused by some type of "monitoring/spy" at their (or your) computer, and a dynamic IP address. it's not…