UPS overcharge for shipping a return items.

Hi everyone, I need your help with this issue, UPS is overcharging me thourgh amazon seller account for the returning labels costs, in some cases when a customer send back the item it cost between 30$-60$ to return it even if I only paid 10$-15$ for the original shipping.

the measurment of my boxes are custom but still I’m paying between 10$-15$ to ship it using USPS and 20$ for using UPS shipping.

There is no much to do, UPS decided what to charge and Amazon let them do whatever they want. the product cost 50$ and in those cases I’m losing money for each return.

Tried to speak with UPS but they only allowed to speack with Amazon becuase they are the UPS’s customer for those labels.

I wonder if it also happens to you and how to deal with it.

In some cases I was able to catach it before, and send a return lable to the customer.

Thank you for the help, hope to find a solution or how to file a claim on UPS to receive the money or part of it back.