Sorry to hear your problems. I had a similar issue with a dealer here in El Paso but luckily for me the other Nissan shop really helped me out. Dont bother calling Nissan Customer Service they will always side with the dealer (at least my experience).

The one shop probably didnt want the other shops problems because it might mess up their warranty index and that makes them look bad. However, that is still strange they wouldnt fix it under warranty. Did you talk to the service manager? Just work your way up till you get to the GM or the owner. Good luck.

Tim