Some carriers might block calls if the call has no caller id in the sip FROM. I stumbled upon such an issue while forwarding inbound calls from FusionPBX to a cell phone number. The calls were rejected if they reached fusionpbx with anonymous as the caller id.
Reusing passwords is never a good idea and by default the fusionpbx setup would use the same user and password for all domains when provisioning.
Offering VoIP solutions to endusers requires the VoIP system to speak their language. Here's how to change the language for the conference system on fusionpx