Who called from 5733033684

I said hello and it was silent for 10 seconds.Then someone says Hello on the phone. I say yes and they hang up instantly.

Caller ID said Charleston MO.  Silent for 10 seconds at least.  Then asked about candidates.  Don't answer.

someone keeps calling frm thisnumber and never says anything

Caller ID  read UNAVAILABLE 573-303-3684, but I answered it, "Hello?"  There was that tell-tale sound of many voices in the background for a split-second; then complete silence for a few seconds; then the many voices sound again, but when they realized I was still sitting there on the line immediately hung up without a word.  Weird.  Why in the world call if you are only going to hang up when someone answers?  Maybe those call center employees have to show a certain number of "connected lines" to earn their money, but their higher-ups can't monitor/prove whether or not they actually speak with anyone at the target numbers.