I can’t see volte option in my iPhone 7, how to enable VOLTE in iPhone 7?

Yes, it does when using a supported carrier who has properly provisioned the line.

The support article you came here from should provide you with the steps necessary to make VoLTE calls on your phone. Chances are you will need to contact your cellular provider to verify that they provide this service in the area that you want to use it with your phone.

Yes, it CAN be out of scope.

As an end user, the response to you is "contact your cellular carrier".

As a service provider, the response is "contact your Apple technical representative". Wait... you're not a supported carrier? Bummer. Contact Apple's corporate headquarters and ask what you have to do to get certified as an Apple supported carrier.

That feature requires carrier support. Who is your cellular carrier and what country are you in?

Where is "here"?

Have you established a relationship with Apple as a supported carrier?

This is a user forum focusing on end users and Apple devices, not service providers.

Your question is out of scope for these forums.