tfung, you are getting the proverbial runaround. Not 10 days ago, I changed AA segments on a CX-issued AONE5 without any hassle. Hang up and try again. Because of the way CX "merges" the RTW desk with the "regular" desk, you have to get lucky to get an agent that knows the RTW rules or has the presence of mind to know that they don't know what they are doing and pass you on to the fare desk for service.