I once knew of a website that would do pre-recorded prank callks of really random stuff. All you do is put in the phone number, choose which prank call you wanted to use, and hit send. The site would call them and play the message. If they tried to *69 it'd just give them a prerecorded message about being pranked(I think).
Wish I remembered what that site was. I never actually used it myself, but I hear that's how it worked.
Supported by wings of faith, Wielding a sword of light. I am a believer.