Is there a way to delete ASIN from Amazon database?

I am a new seller. Say I have products A, B, and C. I have a UPC for each of the products from GS1. When I listed the products at first, I listed it as a generic brand (because i was a stupid newb) and an ASIN was generated for each one. Now, all three products do indeed have a brand (the brand owner is actually the manufacturer and is a friend of mine). So what I did was deleted all of the listings from ‘manage my inventory’ and tried to relist the three products again. Filled out all of the information but ran into error 8541 (i think it is because that UPC -> ASIN link is still in the Amazon database?).

What can I do about this? Do I need to go to GS1 again and buy a new UPC for each one of my products? Is this something that Amazon can resolve through creating a case? Thank you all.