If its a standard pre-ban then the flash hider is just threaded on. You can look closely at the base of the flash hider for a blemish where it was welded, but I don't expect to find one. We only permanently attach flash hiders on barrels that are too short without them.
I bet that the person who answered your e-mail had your order confused with someone else's.
I'd grab a wrench and give her a try (don't use a breaker bar or anything) and she should come right off. If she won't budge with a reasonable amount of force give me a yell and we'll come up with plan B.