long years ago, a buddy and i in tennessee would go get a case of either remington or double A number 8 or 9 for the weeks skeet. we would usually pick up a brick or two of 22 and/or 308, 44 mag, 45 colt or whatever.
by the third time, there would be two cases sittin at the register on saturday afternoon. they got the message.
when you encounter incompetance and just plain rudeness at any of the big stores, simply call for the manager and get it straightened out.
i sometimes have to interact with public or business owners in my line of work. it does not cost me a thing to be polite. it works.