I have a 04 chevy avalanche, when I turn on the cold air the drivers side blows hot air and the passengers side blows the cold air.
You probably have a “blend” door problem. If they are out of sequence you will experience any combination of hot for cold, cold for hot and so on. The dash will more than likely have to be removed to fix the problem. A good, independent mechanic will tell you what is actually needed to remedy the situation.
On several cars, if the AC charge is low, one side will blow hot and the other will blow cold.
What happens when you turn on the Heat? At least you probably won’t need cold air soon.