If it comes on a cell phone you can simply go into your call history and click on the information for that call. A line should come up that allows you to block the caller.
They've been calling me 2-3 times a day. When I answer they say they've got jobs for me. When I say I already have a job instead of being nice like before they just slam phone down with no goodbye nothing. TheN a different dufis from the same number calls the next day. It's been going on for weeks. I feel like I'm being harrassed, it's awful.