I received CP12 and much of the issue stems from their claim of an incorrect social (which isn't correct) - what is the best way to resolve?

They list 
- the Social Security number of one or more individuals claimed as a qualifying dependent was missing or incomplete.
- the last name of one or more individuals claimed as a qualifying dependent does not match our records
- one or more individuals claimed as a qualifying dependent exceeds the age limit
- the amount was computed incorrectly

One issue may stem from several years ago we DID enter a wrong social on the health care exchange.  But that was corrected.  I have one daughter below 16 and one over 18 and in college.