So do roughly 6 billion other people around the world. Whoever solves this problem deserves a Nobel Prize.
There are apps that will help a little, but there is no general solution. See if your carrier has a spam blocking app such as AT&T’s Call Protect. There are also several 3rd party apps, the oldest and most respected is nomorobo. But it’s an almost impossible problem, because spammers can use a different phone number for each call, so blocking phone numbers is useless.
If your contact list has everyone you expect to get calls from go to Settings/Phone and turn on Silence Unknown Callers. With this enabled all calls from numbers not in your contacts will go to voicemail.