Step 1 - ignore the callerID and engage with scammer to get their real number. Because us carriers can't be bothered to tell you where a call is actually coming from.
Even as of last year caller ID accuracy was bad.
Stir shaken doesn't prevent spoofing but it lets terminating carriers validate that the number is legit before sending the call to their customer.
My old team implemented stir shaken for one of the large voip carriers.