I have been getting a call from 520-000-000000 too. I have not answered it and they do not leave a voice message. They have called me twice this week. I am getting really annoyed by it. I wish I knew why this is happening.
It could be an oversea call, my Dad called me from Asia, but instead of displaying the phone number he called me from. It showed a weird number 616-000-0000 which is similar to 520-000-000. Of coz, it could be an oversea telemarketer too, I got one call from a Hong Kong based VOIP >:/
Recieved several calls aswell from the same number but with 12 digits in like this 520-000-000000 and i can hear a TV in the background on the CNN news channel everytime they call. One of the calls had a little child screaming in the background and some spanish speaking person yelling at the child an then they hung up. I have reported this activity to the Department Of Homeland Security as of today. I have had enough!