It's quite easy if it's one specific company. Call them and ask to speak to their regional manager. Once through, inform them that you don't want anymore unsolicited calls and they will take you off their system.

As for stopping calls from recruiters completely, well it's near impossible. That's part of the reason why the vast majority of people can't stand tech recruiters. I don't necessarily enjoy calling people I haven't previously spoken to before but I do try my best to ensure I have a valid reason for calling.