Each leg of the flight has an associated price. You can complain enough and make it one way down on USAir, get a refund for the return. Then book one way back on another airline.

I did this in November when they moved my return flight up too early for me. Told them I had a business meeting which is why I'd selected the later return (which they had cancelled), and that "no" their attempt to rebook did not suit my needs. Took about 20 minutes but I got my refund.

Just be prepared at the airport to show tickets on both airlines if you are asked.....as it's no longer a traditional round trip....gotta prove you are gonna leave their country....lol.