New true-trac differential whine

I got my car back from the shop that replaced the rear end with all new components including axles. There is a "whine" that happens on light acceleration and goes away when off the throttle. I've followed the break in procedures and have about 200 miles on the car since the install. The break in oil was replaced (to see if that helped the noise) and I've put another 20 or so miles on the car since then with no change in the sound. I know that the manufacture says to break in the gears properly, I need to put 500 miles on the car.

I know that the whine can be caused by improper pinion gear depth, improper shims or simply new gears. I asked the shop about it and they claim that they did the installation correctly. My question is: Should I put more miles on the car and see if the noise goes away after 500 miles, or take it back and tell them to fix the problem. I don't want to ruin my new gears if they are not properly installed.