I'm pretty sure it's a premium number scam. They hang up because they hope you will ring back to see who they are. You will then be transferred without your knowledge onto a premium rate call

Started getting calls from this number after signing a Greenpeace petition online. Calls non-stop.

this number calls me several times every day. a real annoying intrusion on my time

Same...they keep ringing...I've also had past calls from Greenpeace. I just don't answer numbers from interstate unless I know them.

I answered today - it was Greenpeace, though I think it's probably a call centre on behalf of a number of charities.

I answered the phone to this number and they hung up - same as Carol stated previously! What a waste of my time!

I answered the phone to this number and they hung up....

this number keeps calling wont leave voice mail message becoming very annoying