I would contact the Extension office or your state Dept of Agriculture.  I would expect within the Extension program there should be someone who is well versed in crop production and use of chemicals.   Ask them to come out and have a look.  Within the dept of agriculture, there should be a dept that oversees pesticide applications.  That dept would be the one to contact if there is a mis-application of pesticides. 

Someone from Extension who is well- versed in pesticides should be able to help you determine what kind of damage you have, and what was the possible cause.  They are not going to be able to work with you to go against the company in question - at least I would not expect that.  However, I would expect they would be able to help you identify what went wrong. If you did anything wrong, they should be able to help you identify that.

Realize that if you contact the dept of Agriculture, and if they come out, the first thing they are going to ask to see is your application records.  If you made a mis-application, then you are in deep doo-doo.  If your records are not up-to-date, you could be in deep doo-doo as well. So, pursue this avenue with your eyes wide open.

One final comment:  going back and re-reading your post, it sounds like your crop is already harvested.  A word to the wise.... if you think you have crop damage, call in an expert BEFORE the crop is harvested - preferably as soon after the damage was done as possible.  Once the crop is harvested, it is really hard to prove that you have damage and what the cause was.   In your situation, you may be too late to do anything about it.