this number has called many times and leaves no message. Caller ID labels them Marin Ctr for I

same as above. calls with no message.  I don't pickup unknown callers.

Called. no message. click click. hung up. I don't answer unknown calls either!

Think it a contractor referral scam.

Total lying scumbags for contractor referral list who claim, when asked why they are calling a number on the Do Not Call List, you are not on the list.  Do not give them any information or request them to do anything. You might wish to give them the address for a local law enforcement office.  You might also ask for their contractor's license number (a contractor must be licensed to solicit work).  No doubt they will give a false number of claim it is not needed.