Email and phone spam also works everywhere. It's time someone did something about it with a whole new system. Calls that are not pre-whitelisted should be blocked and logged. Then at the end of the day, you should get an email summarizing all the blocked calls so you can whitelist the ones you want.
https://www.truecaller.com/ does this to a certain extent. Users flag phone numbers / caller IDs as spam, giving you the discretion to block, whitelist, or subscribe to lists to autoblock common spam callers similar to adblock plug-ins.
