How to stop this type of call?

Can you block " UNAVAILABLE " as the caller's phone number as I'm receiving phishing calls early in the morning when I'm asleep and the caller I.D. says the phone number is " UNAVAILABLE " in addition to the caller's name also as " UNAVAILABLE “.   Is this UNAVAILABLE scheme immune from the requirement to reveal your name and number in order for a call to be allowed to ring through, in other words, unblock caller I.D. and then place the call again?  Unfortunately, UNAVAILABLE as the caller’s phone number allows the calls to come through and then these crooks leave automated scam messages such as mortgage scams on your machine and all while you are (were) still asleep early in the morning.  My landline service is with AT&T Uverse.