F250 power steering not working when still

I have a 2003 F250 with 55,000 miles, with power steering and you can not steer the truck on pavement when it’s not moving. My wife took it to the Ford dealer to find out what it would cost to fix and they charged her $49 and told her it is working the way it was designed which is BS. I’ve tried the steering in another F250 and I was able to easily steer it when the truck was not moving. The unit has fluid, the belt is fine and nothing leaks. The power steering makes no abnormal noises and works fine when the truck is moving. I'd like to know if there's a way to determine if it's a pump problem or a steering gear problem, if I can determine that, I'll just replace the bad part. I'm done with the dealer. Any ideas?

is it a diesel, because it sounds like you have a Hydro-boost system.
Hydro-boost is known for hard steering at a stop. the amount of resistance can vary for truck to truck, things to factor in are 2wd vs 4wd, tire size, additional weight, height, age of vehical. i would not recomend you self diagnose this system, do to the fact that it also runs the power brake system(try stoping a vehical that size with no power assist)
if you are still sure there is a problem, go back to the dealer and ask for the vehical to be rechecked for quality controll by a diffrent technician(at no additional charge)