Flew OGG-LAX last week, 2 days before departure, went online to united.com and paid around $250 to upgrade 3 seats to E+.

Then day of departure went online to change the 3 E+ seats to a different row (still E+). I was charged another $250 as if I was upgrading again.

What is the best way to get the second charges refunded? Fill in the online refund forms? or talk to an agent on the phone? (just tried calling and gave up when the robot voice told me expected wait time was 40 minutes)

thanks,