The most common spoof though is same phone number except the last 4 digits. So I put a tasker rule on my phone to drop any phone number matching mine with a wildcard for the last 4 digits. I have another rule that sends any number that is not on my contact list straight to voicemail.
T-mobile has actually gotten better at detecting spam and spoof calls. About 80% of the spam I get now easily identified as they inject something like "scam likely" as the caller ID. I made another tasker rule with caller ID string matching so those get dropped as well.
Lastly, I play the disconnected number tones at the beginning of my voicemail message. This causes the majority of spam to drop the call and keep my voicemail clean. So now pretty much all I get is rare second or two long voicemail with nothing on it.