Hello,
This article states that "When it’s time for the appointment, participants simply join [...] by dialing in from any phone, and can then carry out the appointment with ease."
Unfortunately the Microsoft Business Support acknowledged that there are issues with the dial-in numbers. A Microsoft Teams Meeting will be generated and a link will be included in the confirmation email, but neither the confirmation email nor the meeting invitation will contain the meeting ID or the dial-in number. Appropriate licenses are available on our site. Dialing in only by phone is therefore not available yet.
Microsoft Business Support confirms that telephone dial-in has not yet been implemented in Microsoft Bookings.
There are also problems with the formatting of the meeting invitation. For example, currently only the link to the logo is inserted instead of the graphic itself. All further links are also displayed as full URL.