Customer Service and case numbers only do one thing, they call the dealership incessantly and tell you the same thing the dealer service manager just told you a few minutes before.
Just a bunch of phone calls by some call center somewhere. Total waste of time, but it does help with documenting the problem.
Replacing the entire defective design
flawed mechanism with the new design is the step they should take, but Chevy is arrogant in their resistance to repair these vehicles correctly. It also seems that the fixes are inconsistent from dealer to dealer and especially from state to state. Demand the new mechanism and see what happens, the animal will show it's real stripes at that point, and you'll know what your're dealing with.
I am on the receiving end of that BS game as well. Also way past the statute requirements in my state as well, over 100 days out of service since January 2012.