I agree with the others. Try again. You don't know who sent the email back to you. I would also offer to provide them with your tax/business info.
You should be able to get somewhere.
Are you buying from a chain store? Because most of them have been pretty forthcoming with the GCC info from what I understand.
Try asking in person at the store level, then try the District Manager, then Regional, then try their head buyer etc... If you are not getting the answer you want keep asking for a supervisor, if that person can't give you what you need ask for THEIR supervisor, etc... until you get to the person who can give you the answer you need. I learned this a long time ago, and though it can sometimes take a lot of banging your head against a brick wall, you will almost always come out victorious.