just make sure you waste as much of their time as possible
I love to make these guys riled up until they start cursing me (real curses! not just swear words) I even started mumbling some curses of my own to one guy and he screamed and hung up
I got a phone call on my cell like that. Some Wog was asking for somebody who had a number close. I put on my cop voice and asked why they were calling and when they asked who I was, I said I was Detective Vic Mackey and that this phone was found on a dead body and demanded them to ID themselves. That guy was befuddled but still refused to ID himself. had him and his supervisor going for 15 minutes before they hung up.
Funny, I never got another call on that phone again.