hi axeria
i'm in the UK and i have a pure winter white hamster from a NHC show breeder who is passionate about keeping pure lines of both winter whites and campbell's. she came with a pedigree which traces her family tree, i suspect if it went far enough, it would trace back to wild caught winter whites.
if you buy from a petshop or hobby breeder who does not show their winter whites or have pedigrees - you will most likely be taking on a hybrid dwarf. i also have a hybrid, and have had 2 others in the past and they are lovely little things
but if you really want a pure winter white, you will need to do your research!