Stopping Phantom calls on an IP phone system
Phantom calls can occur on IP-based phones:
The phone is receiving messages that appear to be SIP calls. If you are connected to an external SIP server (Host), the phone is receiving SIP messages from outside the network. If not, you may have a port forwarded in the router that is letting those messages in. Those are the most common reasons a rogue SIP message can reach a phone behind a NAT.
To resolve the issue:
Log on to the phone Web UI.
Go to “Accounts > Account 1 > SIP Settings (any active accounts)
Check the box for these four settings:
1) Validate Incoming Messages 2) SIP User ID for Incoming INVITE 3) Authenticate Incoming INVITE
4) Only Accept SIP Requests from Known Servers
If you do not use IPVideoTalk on the Android Phones, disable Account 6
If you do not use UPnP then disable that in your router. If you cannot, make this change in each phone
Go to “Accounts > Account 1 > Network (any active accounts)
Change the settings for NAT transversal:
1) If the phone and PBX are on the same network, select “no”
2) If the phone is on an outside SIP server, choose “Keep Alive”
With these changes, you should not get anymore random Phantom calls. If you are still getting Phantom calls, change any ports forwarded to the UCM. It is possible someone is attempting to hack the system.