I had a new air handler and evaporator coil put in in October, 2011 however I just learned that water has been dripping out of the white tubing connected to the handler and has caused damage to the dry wall around the unit. I called the air condition man to come back and look at the system and he said it was a plumbing problem, that the water was not draining. We both didn't understand where the water was coming from because the unit has not been on since it was installed because there was no need for air conditioning. What is happening and who do I get to fix this problem.

If unit has not been running than it cannot be condensate from the coil - yes

Are you absolutely sure it is from the pvc drain that attaches to the air handler. Even if it is dripping I would hold the a/c guy to at least blow out the line with some nitrogen and/or cut it open to take a look.

even better you can do it for 75 cents in home depot pvc fittings and glue.

Own it and find out for yourself