I get these ALL the time, there's never been anyone on the other end.  I seem to get the calls from at least a dozen different Wisconsin 414 area code numbers, all the same behavior, no clue who it is.  Looking at my phone now, I've blocked 13 of these WI numbers (including this one).

My job relocated me to the Great Lakes Region in March and it is pretty sad that from day one with my new cell phone number these calls have been literally bombarding me. At first I thought were from some of our clients (which of course was not). Multiple calls from the 414 area code all with different numbers. Even with call blocking, the calls are too numerous to count on the block list log. I usually let this stuff go but upon all attempts to call back or request to stop it either tells you the number is invalid, or immediate dial tone, etc.
This is beyond pathetic and our National Do Not Call list is an absolute joke as these worthless people doing this are laughing at it the entire time.