Have you already read about the announcement of hotline phones for Microsoft Teams? Microsoft added a new feature on its Microsoft 365 roadmap called Hotline phones. As stated in the Microsoft 365 roadmap feature ID 123749 it enables users on (shared) Teams IP Phones, deployed as common area phones to dial a predefined number.
A Teams Voice Admin can (soon) configure this via Teams Admin Center or on the Teams IP Phone. The use case for this feature could be that users in a open area or common area like a lobby, production plant or else require an option to make emergency calls, call a specific department’s contact under certain circumstances or else.
At the time of writing this, the roadmap mentions that the feature’s rollout is scheduled to start in June 2023. This might be subject to change at anytime, to stay tuned check out the link to the Microsoft 365 roadmap feature ID.