Product Relabeled


I sent in a box of items, all the correct count of each product. FBA marked all items as received under one product. So I had no inventory for most of the shipment, and extra inventory for the one product they put it under.
I requested them all back, and found they had put new labels over my original labels, all for the product they marked as received.
Any thoughts on why they would do this, and how to avoid it in the future?