Incorrectly charged FBA inbound replacement fees

We sent our shipments to 5 FCs and we shouldn’t be paying for any replacement fees. However Amazon charged us. I contacted seller support. At first they say it’s incorrect charged and they will raise a reimbursement ticket. Ah there goes my nightmare of every support to either coming in with irrelevant copy paste information or claim that we opted in for partial split to send the shipments to more than 3 FCs (we sent it to 5 not 3).

I asked them to provide me with proof that we opted in, and they started going circles, only saying the fees are legit.

What do I do at this point?

I even started to question myself, did I opt in? How do I find it out?

Thank you. And I hate Amazon seller support.