At the beginning of this year, I had a lot of fake calls. What helped was blocking the numbers when I discovered it was a fake. They tried several days while they were blocked and it stopped. Then they tried a new number and I blocked them again. After a few weeks, they stopped calling and they haven't done it since then. If you don't want to answer the calls where you don't know the number, just reject the call, google the number and have a look at the owner or if someone says it's a fake. If it's a real person you can call back.