There are many scenarios where we need to block on the tenant level : Anonymous calls , Unknown calls , or calls that comes without calling id , more than that , we need sometimes to block pattern numbers from calling our services numbers , or even our teams users.
for this , Microsoft has made it possible to block inbound call numbers , at the microsoft tenant level :
New-CsInboundBlockNumberPattern - adds a blocked number pattern to the tenant level. Inbound PSTN calls are checked from a number that matches the blocked number pattern before routing the calls to users, and if the blocked pattern is found, it will be blocked.
to give an example i will block my personal number from calling any service or user on my tenant
Once you have configured the block number pattern, you can validate it on the "Get-CsTenantBlockedCallingNumbers" , it takes normaly from 5 to 10 minutes to be operational :