Keeps calling a hanging up!

Same here.  Answer, then after about 15 seconds of dead air, hangs up.

Rang twice then hung up, from NC. Thanks to the new iphone software you can now block these types of calls.

Been getting several of these calls lately and no voicemails have been left.

And yes, the newer iPhones do allow you to block individual numbers - my old one didn't have the capability (3GS) but the 4 and above models do (I currently have a 4s)

If somebody can't be decent enough to leave a voicemail, I don't return the call.  I've had way too many horrid Indian accented people calling me with fake American names making just about every threat under the sun - no more.

Just easier now to search the phone number and see who it is and, if necessary, I can block.

I got a voice mail with music and then hang up. Is there a way the cell phone companies can block these calls. Going to find out today.