Looking for some advice on how to take the following forward.

My carrier UPS signed off 3 packages as delivered to Amazons FBA warehouse in Italy. Each package contained 250pcs.

The shipment closed on Seller Central as 2 packages and only 500pcs of inventory received (1 package missing)

I raised a dispute in seller support and received the following response. Has anyone encountered a similar situation and any advice or suggestions how I can challenge?

I would like to inform you that after a thorough search we have verified the contents of the shipment several times, it has been counted and confirmed as from the beginning, when the items are marked with the words 'Investigation completed', it means that we have physically counted the units at the time of receipt. In these cases, when we start receiving the goods at our logistics centers, we first associate all the cartons received with those provided according to your shipping plan, then proceed to physically count all the units stored.

When all the cartons have been correctly matched and the physical count has been completed, the items are marked with the words “Investigation completed: shipment content counted and confirmed” in Seller Central.

In the Content tab of the shipment summary in Seller Central, the following items will be displayed: * the “expected units”, that is, the total number of units expected based on what is indicated in your shipping plan; * the “units identified”, that is, the total number of units physically counted and validated by Amazon, including the units already reimbursed; * a “discrepancy”, which indicates any difference between what was announced and the units actually received, count and validate; * a 'status', which indicates whether or not the discrepancy has been confirmed by part of us and the possible actions it can take for reconciliation.

In response to your request, we have completed a further verification and can confirm that we do not have any records regarding the receipt of the units in question, as you opted for a non Amazon-partnered carrier, we cannot provide reimbursement for these items.

This also applies in case you or the carrier possess a confirmed receipt of delivery, but Amazon does not have any record of physically receiving the unit.