This is the third time this month, the person is selling coins.I could  not under his name or the company he works for. He does not leave a message or has he sent me information on the company  in a January conversation With the caller. I am   getting way less calls then before I had it

How do I block this number from calling again?

Google is your friend.
Try "phone blocker"
(Without the quotes)

I received a call from a guy who said his name was David (clearly a foreign accent).  He said there was a problem with my computer and Windows 8.  He said I had to turn on my computer right away so he could help me correct the problem.  I said, "I hate to disappoint you, but I don't have a computer!"  He continued trying to tell me I did.  He asked if I've ever had a computer with Windows 8 in this household.  I told him, "No!"
I hate these calls especially when I'm on a "Do Not Call" list.

Consider maybe getting a call blocking device or phone.. You can google them and many are around $60.00 or so.