balky downshift

I'm in my first week with a new '05 Elantra GT AT. The car seems to be geared for good gas mileage, which is fine with me. But when the transmission gets to 4th (high) gear around 40 mph it really, really seems to want to stay there. RPM's can drop to 1500 or below and I can feel the "lug" on any kind of upgrade. Even "punching it" doesn't necessarily bring on a downshift. Obviously I can shift to third myself - but that seems to miss the point of driving an automatic - which was a major goal of mine after over 20 years of clutching.
Is this a normal characteristic of this model - or do I start haunting the dealer about it?

give it time, the TCM will learn your drive style and will start to shift accordingly. In the city, below +-75kmph (+-45mph) keep the g-lever in "3".

Thanks for the advice. I've been doing my own shifting so long that I'm having a hard time trusting the machine to do it for me... In all other respects this is a fine automobile!