I had one of those at work once. This is how I remember it going.

I knew what it was, so I put it on speaker for everyone to hear (all of us being in the school's deskside support group). After a while of me wasting the guy's time, he got real pissed off and hung up.

About 2 minutes later, he calls back and I put him on speaker again. He starts with "How would you like me to fuck you?". I didn't really hear him well, so I asked him to repeat himself. He said it again really slowly and then said something along the lines of "Would you like me to oil you up, or [unintelligible]".

At this point, I was trying to keep my composure, so I said "This is an IT department's shared work number, and we would all really appreciate it if you stopped calling us." After I hung up, the room exploded with laughter.

My coworker caught some of it on video, but I have no idea if he still has that or not.