Sorry for the confusion here, can we clarify the issue here?
Is the issue with outgoing or incoming?
Our technicians have doubled checked your number specifically and have deemed it 100% operational.
You made one successful outgoing call, the rest were dialed in the wrong format. Please use this format.
Incoming issue seems to be coming from fritz box. We are not doing anything different here, the difference between x-lite and receive the call with fritz box should be none.
We also see you connecting to SIP device Z 3.9.32144 r3212 without issues. Its a config issue or perhaps firewall/netowrk related. Perhaps there is some more here here regarding the issue