Can I silence unknown callers on Curve 9330?

Hi, I am having a problem with my phone and I have a couple questions that hopefully someone can answer. Lately I have been receiving calls from what seem like random numbers that ring and when I answer, the call is disconnected after a second or two. Other times there is someone on the line asking for a name I do not recognize claiming the call is a follow-up to completing an online survey or something. It has been so bad recently that I have been receiving calls every day (I think I have had 5 or so just today). Usually when I call back a recording plays claiming that the number is not in service. When I do reach a person, they usually just hang up when I ask to no longer be called.

Has anyone else had problems with calls like this? Since this is a private number and I don't intend to answer calls from unknown numbers, I would like to silence the ringing (or, better yet, send to voicemail) while still receiving calls from numbers in my contacts. Is there a way I can accomplish this on my Curve 9330?

I use Be Buzz Pro, and all notifications (audible) are off, except for the selected contacts I have separate tones and different flashing LED colors.