Brake Disc Caliper problems of the 2001 Nissan Pathfinder

We purchased a new Nissan Pathfinder (VIN #jn8dr09y61w608169) in July 2001 from white plains Nissan, inc. In white plains, NY. October 12, 2003: the car began making a screeching noise when braking. I removed the front right tire to see what was going on, and immediately saw that part of the caliper broke off, and was leaning against the inside part of the rim, at which point I put the tire back on, and began calling Nissan to set up an appointment (the car is still under original manufacturers warranty). October 13, 2003: we took it to the local Nissan dealer in stamford, stamford motors, inc. , Nissan division. When my wife olga dropped the car off at the dealership, she stated clearly what the problem was (broken caliper) and asked how long it would take to get it fixed under the manufacturers warranty. She also pointed out that, according to the piece of paper given to her by the service representative, she could get charged for the time to diagnose the problem, while it was obvious what the problem was. The dealership representative said it was standard procedure, and she had to sign it. The following day, nobody contacted me or my wife and we had to call ourselves. When my wife called the dealership for an update, their service manager steve berman said that the part wasn't going to be covered, because they think that the part had been tampered with. When my wife asked mr. Berman to elaborate, he said that these parts rarely break unless tampered with, and because there was a scratch on the outside on the caliper, they think that someone was trying to change the break pads himself, and broke the caliper.  we have already shown the part to several independent shops, including a metal expert, all of which recognized a fatigue failure and not something that could have been caused by tempering . We are intending to pursue this matter further, until Nissan decides to take responsibility and fix this very serious customer care issue.