Whenever you get a new bike, make sure that the rear derailleur travel limits are set properly, and check them regularly. On new bikes the cables stretch a bit over the first miles, and the clearances on some parts changes as they break in. The bike was probably within spec when it was set up, but loosened up after some riding. With luck, the shop will probably take care of the problem, but you should be sure that you know how to check and adjust the clearance on the derailleurs, the brakes, and how to fine tune both. The mechanics at the shop can show you how.