Hi Mythlea,
I understand that when you connect with your Bluetooth headphone, it passes the test call but it doesn't pick mic when in the call.
Not all Bluetooth headsets are compatible with MS Teams, so Microsoft worked with device partners and come up with Teams certified devices to market, and they continue to bring new:
https://www.microsoft.com/en-us/microsoft-365/m...
Certified for Microsoft Teams: Devices certified at this level indicate, for a no-compromise Teams experience. These devices offer all of the benefits of prior certification and also include a dedicated Teams button with LED indicator. With most form factors, the Teams button will be an easy-to-find tactile button with the Teams logo. Microsoft continues to work with device manufacturers to deliver new value via firmware updates over time.
https://docs.microsoft.com/en-us/microsoftteams...
When I looked into it further, I found some UserVoice where similar issue discussed, I would suggest to participant in UserVoice and report your bug directly to Microsoft Teams forum for improvements to the developer team:
https://microsoftteams.uservoice.com/
Similar UserVoice:
Please let me know if you have any further questions on this and I will be happy to help.
Regards
Nik