Transmission Not Engage problems of the 2012 Volvo S60

When at a full stop, with foot on the brake, on a hill and in gear (drive) the car rolls backwards when removing my foot from the break pedal. The transmission does not engage unless the gas pedal is depressed. The Volvo of san diego "technician" checked a 2013 vehicle with the same transmission and found the same problem. Unfortunately, he used this test to prove that this was normal behavior for this vehicle, and thus, the transmission was in fine condition. . I don't see how a car rolling backwards while in a forward gear could ever be considered normal behavior. It is at best, a defect, at worst, a safety issue. Volvo of san diego refuses to fix the problem. It should be noted that this car has only 46,000 miles, and is still under full warranty. There are other issues with this transmission, but they are difficult to describe in this format, but the problems were verified by the Volvo of san diego person who went on the test drive with me, on June 15th, 2016. This is an ongoing issue which I have been describing to Volvo of san diego since December 2015. To date, they have refused to even acknowledge that there is a problem.