Bug maybe in Teams app for Desk phones

TacoCatMouse 

Since the community has not yet responded to your post, you might want to contact https://support.microsoft.com/en-us/topic/global-customer-service-phone-numbers-c0389ade-5640-e588-8b0e-28de8afeb3f2 directly or open a case at https://answers.microsoft.com/, where there are authorized Microsoft agents available to help with further troubleshoot with you until your issue is resolved. 

Since the community has not yet responded to your post, you might want to seek assistance with other resources that are focused on tech support:

• Ask your IT manager to open a support case or call Microsoft using the support line you were given.  Other options for business subscription admins are listed here:

https://docs.microsoft.com/en-us/microsoft-365/business-video/get-help-support?view=o365-worldwide#:~:text=Online%20support%201%20Go%20to%20the%20admin%20center,contact%20method%2C%20and%20then%20select%20Contact%20me.%20

https://support.serviceshub.microsoft.com/supportforbusiness/create

• Additional tech support is available at https://support.microsoft.com/ or https://answers.microsoft.com/, where authorized Microsoft agents are available to trouble an issue until it’s resolved.