Awkward Piyo.
If a number is not in my contacts, I just silence the ring and don't reply. I do however google it and check whether it is a telemarketer, and 99.9% of the time it is. Sometimes though when I'm in the mood and do know the number is a salesperson, I reply, let them launch into their marketing speech and put the phone aside. They deliberately chose this as their career, so it is upon them. I'm helping them along towards quitting their McJob and getting a real one.