OK correct me if I'm wrong, if I remember right you need to program the phone to reconginize the extender *?? or #?? I cant remember the code. you know it is using the extender by the double beep when you dial or answer a call.
I have 4 verizon phones 3 are on my account and the fourth is a work issued phone. I have each one of my phones programed to recongize the extender, and I hear the double beep when ever I use one of the phones in the house. The work issued phone is not programed, and does not give me the double beep, and the service on that phone is not that great even if I'm standing five feet from the extender, which makes me belive it is not using the extender.
Course I could be wrong. First time this year
Another thing you could do is go into your router, and set a bandwidth usage rule on the port the extender is connected to.