I have had that happen too although it was Customs who mandated that I had to hire a "customs broker." I went ahead with it because I was going to be out of town for a few weeks and did not want to leave my gun in an United airlines warehouse for 2 weeks.

I don't know what Forms are needed for pre 1899 as my gun was post 1899. I think though that the ATF Form 6 states on the backside that a "customs broker" is not required. So if you had to fill out a Form 6 you might want to take a look at that.