I have a Meile dishwasher, and its very quiet, I have a friend who has a washing machine and dishwasher which are quite ancient and they are also very quiet even now. There is a problem with proving what you all said at the point of sale, but even if noise had not been a main factor for you, the fact the person that came out said it was noisier than it should be, and actually took steps to try to stop it, should be in your favour that the machine is a noisy one anyway. To me, excessive noise when working that is unusual for that make of machine, means something inside, either with parts or construction, is not right and this could well alter the length of working life of the machine. If the shop won't take it back, CAB or trading standards is a good next step.