Cur non isti mictum ex occasione?
I tried "you sound hot, what are you wearing" and 'Brian' hung up. My wife though was unamused.I think they just detect that the call was answered.
If so, then it will either hangup and put on the 'working number to be called later' or send you to an IVR when you can press '1' to chat a CSR where the well worn scam dialogue starts.
I used to get quite a few and they have tapered off lately. I do enjoy leading them on and wasting their time when Bruce from the subcontinent calls.
For a quick hangup, ask how is everything in East Bengal today, or ask them if they mind if I spank the monkey since I really do get aroused during these calls. Works a treat.