I fixed this by "copy settings" from another working ext. But I still don't know what made this happen. Ext 12 would ring(intercom) every 30 mins, when you pick it up it would rapidly dial 6 digits.. then dead. The intercoms also sounded like dial tone, even with no lines.
If you call another ext. from 12 it rings in as "voice messaging system".
What am I missing?

What a strange world we live in...