We got hot air in the driver side, but only cold air in the passenger side why? on 2003 Toyota Camry

I took the car to the dealer and charge me for an hour labor and they could not figured it out. Only one side work for hot air, for the face and feet.

Asked by for the 2003 Toyota Camry
very poss actuator issue.very common these days,try another shop that dealer is not very ____
I took it to a mechanic also and he could not fix it either. I can't believe they cannot figure this out. Sounds kind of a simple concept. The car gets hot air, but only in one side, the other side gets only cold air.