OP, I sense that your current reservation now has a notation, inserted by the first agent that you had talked to, with the false information that you cannot change the intl portion. The later agents might just be echoing off of it without actually checking into thel rules themselves. I would either call back, request to directly speak to a supervisor, and refer to the fare rules that someone generously took the time to post in this thread, or email UA and ask them to review your PNR. Good luck.