Had four calls in past 2 weeks, First two got no response when I said "hello". After two such events I add them to a separate call blocker unit I found on Amazon (about $100) and it does the job. If I am home I may hear one short ring and they are disconnected but I get a record of the call.  If anybody thinks being on the "DO NOT CALL LIST" will solve this type of problem you are sadly mistaken. The call blocker is much better than Verizon which only allows 10 blocked calls and you need the exact number. This unit has many times that amount and it allows wide card numbers.

Old man wanting to do an environmental survey

Picked up phone after one ring and they hung up before I could say a word.  So it was not like they heard me and decided it was a wrong number.  Don't know why they do this?

No voice on other end when I answered.

called today. Caller id "Bradenton FL". hung up when answering machine picked up. I'll lay a bet that it's one of the "free security system" scammers...........