Incompetent Seller Support Team

The Seller Support Team is becoming increasingly incompetent and are unable to resolve a simple standard case.

I opened a case for inbound shipping units that were lost in the Amazon warehouse and requested an investigation after sharing the proof of delivery. The Seller Support Associate refused to launch an investigation. When I reshared the proof of delivery, he started sending me the same copy/paste response multiple times until eventually he decided to ignore me.

Where can I reach out to report such an incompetent Associate?