2010 Other Nissan Models Check Engine Soon Light. Battery o

I bought a brand new Nissan Rogue 2010 with 11 miles on it. The next day I noticed that when I pushed the gas there was not much power. By the 3rd day the car was barely moving, even though I was flooring the pedal. I took it to Nissan, (who said they would do nothing for me!), And the code on my diagnostic was P1778 and P0715, both of which point to transmission. They told me it was a low batter, but I was told by 5 other repair places that it wasn't a battery issue. I am so confused on what to do! Even in the report, they just said reset history of low voltage. They didn't even say they charged the battery. ON A BRAND NEW CAR! What do you think the problem really is? Do I need to get it serviced somewhere else? Please help!