Back in the early '70's, I was a manager of a Braum's store and all but two of my employees were ladies. I informed them all that if they took a call for a call-in order and it was an obscene call, to get my attention and then give me the phone. I would then stand there and let them ramble, just before saying, "Fellow, I'm sorry, but you just aren't doing anything for me."
That was ALWAYS followed up with a grunt and a hang-up. Can you imagine the "trash talker's" feeling after realizing that they had been talking dirty with a guy?
Haha! I worked at a McD's that used to get prank calls regularly. Us girls used to just cut the guy off in mid-sentence with "OH, MY ... OMG!! OK, I'm done now ... THANKS!" and just hang up. It would usually take the guy a couple of hours to work up the nerve to call back. After a week or so of that, he finally quit calling ... (BTW, we figured out who it was pretty quick ... One of the cooks gave himself away pretty early on, so we would talk in front of him about about how little that guy's thingee must be and how bad he must smell for him to have to resort to diddling himself on 30-second phone calls ... )