If you want to change a SKU from being FBA (Fulfilled By Amazon) to being Seller Fulfilled, you need to go into the FBA Manage Inventory Tab in Seller Central and delete/archive those SKU's.  Then they will no longer have inventory sent to us as FBA sku's. Then delete the SKU in the Amazon FBA tab (Shop --> Fulfillments--> Amazon FBA). This will set the product to be a seller fulfilled product and as long as the inventory in Amazon.com stays at zero, the product will remain so.