Same here. They must have just started using this # for spam calling. The reason no one answers when you pick up is that none of their agents are available to answer their end of the call. Their automatic dialer is dialing as fast as it can and if someone picks up and someone in the "boiler room" is available they probably will pick up. Otherwise it goes dead and they probably put you on the call again list as they know it is a good # and someone there might pickup the phone.
I just switched my VOIP phone service from Vonage to Ooma. One of the reasons was because Ooma has a really great call blocking service. It is also a lot less expensive. Ooma has community blocking where they block out known telemarketers and a personal blocking list (you just go through your call record and click on the #s you want to block). Either list can be directed to voice mail or sent a # has been disconnected message (among some other choices).