Amazon changed my ASIN

I created a new listing with a unique SKU and unique UPC, and Amazon assigned it a new ASIN. I created a shipment that included this ASIN (it appears correctly on the shipment packing list), and sent units for it along with other products.

At some point, Amazon removed the original ASIN and reassigned the SKU to one of my existing products (a different ASIN). As a result, when the shipment arrived:

* The units for that SKU were received under the wrong ASIN.

* The original ASIN no longer exists.

* The entire shipment is now mixed up — all products were received, but not under the correct ASINs.

* None of the units are showing up under the right listings in my inventory.

* Has anyone experienced this before? How can I fix this and make sure my units are correctly assigned to their intended ASINs?