Create a SPAM WARNING when spoofed PSTN inbound calls match a number within the RC Tenant

We have had instances where inbound PSTN spam caller ids have matched numbers within our RC tenant. This has resulted in instances where individuals believed their supervisor has called them when they did not.

A call within a RC Tenant to another number within the same tenant should never originate from the PSTN, these are station to station calls. When a caller ID is presented that is within the same tenant, can the caller ID be flagged as 'SPAM Warning', or even blocked altogether, as the call has arrived from an apparently invalid direction?

This mimics SPAM Warnings done by cell carriers. In our case it is potentially consequential as the spammers are clearly leveraging trust relationships within our organizaton.