I'm confused as to why you involved UA at this point by purchasing the ticket through them, I think that will be a mistake in the end. AC as the operator could've accepted the ticket or AZ could've corrected the problem - those are the two carriers involved with the dispute, but now you've involved UA and I don't believe you have anything standing to deny the charge to your credit card company.

I would pursue this with AZ as the ticket was printed on their stock and they made the changes and affixed the stickers, etc. G'Luck.