For the record - the Call Monitor is not part of TR064 protocol. It is an AVM specific feature. In upcoming OH3 the fritzboxtr064 binding will be replaced by a new universal TR064 binding which for example supports modified (branded) products like Telekom Speedport as well. As of OH2.5.9 the Call Monitor has been moved into the avmfritz binding. If you like to add useful information to the docs please it would be nice if you can do it over there.
I just found the Reason. While do the change, looks like he grep an fork for my own and not push it to review to main fork.
Don’t habe the time to look and read the docs how to get it pushed back to main :-((( Sorry.
I just entered (after Dial Informations to activate and deactivate Call Monitor in Fritz) the following: Please be sure, that your openhab Server accept new TCP Connections from your FritzBox from Port 1012 in the firewall.