Need someone skilled in Telecommunications and Electronics

[EarlyDawn]

Here's the situation. About two and a half weeks ago, my (now) ex-girlfriend initiated a breakup over a meaningless argument that was really just an excuse to break up. Over the last two weeks, her annoying, immature friends have been non-stop calling me and generally being annoying bitches. I obviously can't threaten to kill them, I don't know how well that'll go over. So I turn to you, fellow PSUers, I'm sure at least one of you has been in a situation like this.

Stuff you should know:
Changing my phonenumber is not an option. My parents, particularly my father rely on the line for business calls.

I'm not actively provoking conversation from them in any way. I ususally pick up, listen to their high-pitched screaming and then hang up.

They refuse to leave messages.

What I'm looking for:
A- Some way to block a phone number. This is not an ideal solution because, being annoying teenage bitches, the ammount of phones they have access to probably equals the number of STDs they carry.

B- Some way to effect their phonenumber or somesuch (phreaking). Something that will send a clear message.

C- The proper course of legal action. This too, is far from ideal. I want this handled as small as possible.

Thanks PSU.