Who called from 4152004960

Recvd call from this number, asked for someone in our r&d dept. I called the number back and it said it was disconnected. You are going on my reject list!!!!

Answered call, nobody talking or acknowledging.
Called back - number out of service.
Current CallerID app attributes the number to be suspected SPAM.

Unsolicited call

I just got a call from (415)200-4960 and the person did not answer when I said hello.  I get at least 5 calls per day from telemarketers or people phishing for information.  I never give any information and yell into the telephone not to call me again.
Next time I plan to make them deaf by using a loud whistle.  
Any ideas on how to prevent these idiots from calling?  I think they just ignore the "do not call.gov" website.

They said something about sending a white paper. I told them to take me off their list. They called back an hour later.