If you don't need the money right away, I would suggest you login to your Western Union account, fill out the form for the transfer, and just do NOT click on the Transfer confirmation. Exit the site or app. Chances are, you'll get a promotion code for a free transfer or a half off the transfer fee through email within a few days.
If you're not physically in Argentina now, of course you can do the transfer at a much lower fee by filling out the form online and bringing the cash to a local agent instead of paying with debit or bank transfer.
If you are going to pay the full price WU transfer fee right now, you might as well just pay with a foreign credit card that has no foreign transaction fee. The transfer fee basically negates the higher exchange rate between the rate you get from WU and foreign credit card MEP rate.