Who called from 9280000000

What is up with all these zeros???  I didn't answer, and no message...goes on my Blocked #'s list

repeated calls no message left

I answered the phone call and in a robotic voice it said " we are watching we are anonymous " and then it was silence for a few seconds and they hung up and right afterwards my phone told me that Facebook was using my location and it wouldn't let me get into my Facebook app to shut it off I had to shut my whole phone off and restart it