How to handle this product issue

So we have a brand we buy direct from. They have zero desire to do anything with Amazon themselves. So it’s up to us. Sadly prior sellers in their sloppiness used the products UPC’s to list items as case packs and not the single units. They are items which would only really sell as singles.

What would be the best way to combat this. We do not have brand registry on this brand, and neither does the brand. So editing these listings will don’t be likely.

Should we apply for a gtin exemption as a workaround or just bug seller support to maybe change these to the proper item?