Who called from 4123572608

Recieved call no one answered pushed # sign several times? read somewhere that discourages callers?

Monday, 5/28/12, Memorial Day, received a call from:
"Unknown Name  412-357-2608" ,
shortly after 12pm, to my Pittsburgh landline that is on  "Do Not Call List."
No message.  Think they may have called previously, and when I would answer,
they would say nothing.

Why do I get calls from the ymax communications test number, that's who answers on a recording.

call received 5/28/2012 at 3:41 pm  left no message. I returned call at 5:26 pm to answer mailbox full

calls without answer