When trying to transfer an incoming call to my colleagues I am often unable to. While in the call, I push the Transfer key and then the key for whichever office I am wanting to transfer to. The call is returned to me immediately after displaying a message at the top of the screen "Emergency Calls Only". What is causing this and how do I fix it without having to reboot my router every time as this causes my system to be down for too long a period - especially when it happens several times per day?
Do Not Disturb is not activated on any of the phones at the time.