air conditioner blows hot and cold air when it is supposed to be just cool air

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My air conditioner blows hot and cold air. The cooling is very uneven. I have just spent $870. and it is just as bad as it was originally before they "fixed it". 2 valves were replaced, one high pressure and the other one was low pressure. Very disappointed . It was probably something simple like needing freon....but was told it needed all this expensive parts. I am afraid to go back. I had some cooling before the repair but nothing like it was supposed to be. I am the only owner, and it had never been recharged.