Impossible to correct Brand?

I made a listing and made what is apparently a catastrophic mistake-

I had the Brand as “Generic”, because i was in the process of getting my brand registered to Amazon. Once it was registered, I found out I cannot just simply correct the brand. So I deleted the product entirely, and started over just to find out that I cannot re-add the product with the new (correct) brand name, because Amazon recognizes the product name, says it has an existing ASIN, and won’t let me add it with a new, different brand name… I’ve been going in circles with Amazon’s completely unhelpful customer service telling me to do what I already did again.

I have FBA inventory in Amazons warehouse. Its an existing brand name product labeled with its own SKU, so there is no ASIN label required on the products, so no issue there.

How in the actual hell can I get this fixed and have the Brand name corrected?

Thank you for any help.