Hello, friend!
Generally, the device needs to register with the carrier, and the voice data needs to be provisioned with the carrier.
If you are an enterprise user, you need to configure a SIP server, use an asterisk (*) as an open-source, and can make calls between extensions. If you need to connect to an external line, you need to register with the IMS platform of the carrier. The extension number needs to be planned by yourself.
For more information about the MA5616 configuration, click:
Service Configuration
Thanks!