I'm guessing most scammers don't even hear your prompt. I have a simple, short, "leave a message <beeep>" prompt and the vast majority of my scam voicemails go:

I'm guessing most scammers don't even hear your prompt. I have a simple, short, "leave a message <beeep>" prompt and the vast majority of my scam voicemails go: 0:00 - 0:10: silence 0:10 - hangup: "Hello? Hello?"