How do you block unknown phone numbers on iPhone 7?

I've been getting unknown phone calls from marketing people and people from other country's and it's annoying the f***king hell out of me. My dads been getting the same thing. Now I'm not sure weither to believe it or not but one of my dads friend told me that the president legalized phone marketing for making business. Weither that might or might not be true I would still like to know how to block these f**kers from calling me.

You canr

There are 4 bazillion call blocking apps

Click the (i) on the rhs next to the number on recent calls

scroll down -> Block caller

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