Who called from 2311111111

Keep getting 2 to 3 calls per day from 231-111-1111. when I answer the phone it is silent. When I call back I am notified this is a disconnected number. How can I block this number?????

May come across CID as (231)111-111. Same old alarm/medical alert scam. Robo, female.

231-111-1111 called my cell, which is on the national and state do not call list.  Silent when I answered. Am reporting but not sure that does any good.

Received call from 231-11

Received call from 231-111-111, which is not even a real phone number. No voice mail was left. Blocked.