Re use my old barcodes?

I have a GS1 account and indeed I have had it for many years. As such I have barcodes for things I deleted from my amazon catalogue years ago.

As I begin to approach the end of my GS1 allocation I will need to buy more codes…

But what of these old and now disused codes? When I tested today with a listing I was not surprised to see that amazon still had the code registered. So I could not reuse the code. Even though I can change what it says on Gs1 (sku etc)

Is there anyway I can get these numbers ‘cleaned’ so I could use them again? or once a number has been used to build a listing is that it?

Any and all help is much apprciated