Hello,
Need more information on your configuration for the same. Looking at the response I am assuming that you are using a Teams Direct Routing set up which utilizes you local SBC. When the calls are getting forwarded can you check the Port Numbers and the IP address which is being used by the SBC is whitelisted and SBC is properly configured.
Additionally can you also check if you SBC is not enabled with LBR services on the SBC and on the Microsoft Teams Tenant.
With Regards,
Satish U
