Hang on a minute!
Before we go spending huge chunks of cash with your local dealership, there's something you can try.
is a learning computer (much like Arnie), and I experienced the exact same thing with my auto 'box (Aisin Warner SU1-002).
The gearbox uses some weird compter trickery to "guess" what you're doing, and if you've been driving enthusiastically, it does behave differently...it holds gears for longer when accelerating, and it did drop down through the gears when you're braking to help you slow down...if you're driving normally, it just changes up and down as normal.
Mine did this for the entire three years that I had the car (including the "jolt" when changing from 2nd to 1st when cold), and never had any problems - I think this is just the way the gearbox works. You can try unhooking the battery for half an hour to "reset" the
to factory default, which I believe resets the gearbox too.
I never used to worry about it - didn't break in the three years I had the car.