Welcome to SaleHoo :)
I think you may have found yourself a scammer and not a legitimate supplier. As far as I know bank details are not a requirement, some suppliers may require that you provide them additional info like your tax ID or business license but I have yet to come across one that requires you to provide them your bank details before allowing you access to their wholesale prices.
By the way, where did you find this supplier? I certainly hope not in SaleHoo.
I recommend downloading your copy of Link hidden: Login to view
to help you in contacting suppliers the right way :)
Hope this helps!