Blocking Caller ID – Does it cost money?

Well, firstly, my friend has Caller ID and we are mad at each other right now, so she won’t pick up the phone if she sees it is from me. I know there is a way, but doesn’t it cost money? I live in California… and I just want to do it for a single call.
OH- and do you have to HAVE Caller ID for this to work?

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