Log in to the 3CX PBX WEB interface as an administrator
Go to menu SIP Trunks
And click Add SIP trunk button
SIP trunk settings
On the same page, just below…
Enter the username and password obtained during registration
Authentication -> Authentication ID (aka SIP User ID): USERNAME
Authentication -> Authentication Password: PASSWORD
Add default caller ID
Enter OK and reload the page to verify that the trunk is registered.
Add Outbound Rule:
Outbound Rule -> Add
On the same page, just below…
Make outbound calls on
Outbound Rules successfully added
Add New Extensions
Next, you can enter the WEB phone at https://3CX-IP:5001/webclient
And dial the number with the prefix 00