Changing ASIN from "Generic" to my newly Approved Brand

Hi, I saw some other posters with this issue - not being able to convert a product listed within 'Generic' to a brand name. The advice is to create a new ASIN with the newly approved brand. I understand that a new ASIN has to created.

However my UPC/GTIN are linked to my products that were listed as Generic, even when I deleted those same products listed as Generic, Amazon is still finding them when I try to create a new listing under my recently approved Brand.

How can I re-use the same GTINs that are linked to my old Generic products that I DELETED already?