You can register a calling bot for Microsoft Teams. This bot can participates in audio/video calls and online meetings.
There's a new version of the Teams app manifest with two additional settings, supportsCalling and supportsVideo. These settings are included in the Developer Preview version of the Microsoft Teams app manifest. Check the setting in the manifest.json, then you will see,
bots[0].supportsCalling. If this is present and set to true, Teams will allow your bot to participate in calls and online meetings.
Here's the related documentation.