Called again. no luck. The agent this time is very helpful but still said that this is a codeshare flight so cannot redeem. Anyway, don't want to fight. May be look for other alternatives. One thing I don't understand... He can check the seats availability but then said he cannot book because of the codeshare. When I check the American Airlines website, it is not show as a codeshare. If I have AAdvanage, it can redeem, anyhow.