Who called from 4804967541

My oldest son got several calls from this number. They don't leave messages, and he does not pick up as he is paying for the minutes. Who this is and how to stop the calls?

Did not leave message - keeps calling and using my minutes

Has called our number 3 or 4 times. Does not leave a message and does not answer. Uses our minutes. Last call was about an hour ago.

I get calls from this number every so often.  I don't answer it, who is this?

Caller unknown. Does not leave a message.