There are few alternatives to block such calls. May this options in the link below will help you.
http://vontech.blogspot.com/2012/12/vonage-specific-call-block-feature.html
I started receiving calls from this number a week ago. They are calling my work number. It says Vonage on the Caller ID screen.
They don't leave a message. They do however, sit on the phone for awhile. In the first message I heard Classical music in the background. The second message I heard was this weird deep and slow breathing.
Vonage is terrible. Magic Jack is exactly the same thing and for hundreds less a year.
I used to be a Vonage customer. I guess they want my business back. I would assume they are dying out.
cellbust.com
Calls all the time I will not switch to Vonage. Stop calling me! I try to call back to tell them to stop and I get this " the number is not in service"