Auto air conditioning?

Took my vehicle in because the air conditioner was running warm. They said my fan needed to be replaced. After this air still warm, starts off cool and them warms up. Took it back again and was told something or another had to be reset after fan was replaced. Still the air is warm after all of that. They said nothing is wrong with the compressor. Does somebody have any idea what the hell is going on here??!! No wonder GMC dealerships are going under with the dumb azz mechanics they employ.