Poor service and incompetence from DHL

I wanted to return incompatible equipment to Amazon USA. From the Amazon USA App I received a waybill with a link to DHL to schedule a pickup. After completing all the paperwork as per DHL instructions the parcel was collected. Two weeks later the parcel was delivered back to me without any communication or explanation. After several phone calls and emails, I have still not received an answer as to why the parcel was returned. Now it seems that nobody at DHL knows how to get the parcel back to the USA. The electronic systems do not allow me to reschedule a pickup or recreate a waybill for the same parcel. I could not find a Customer Service hotline or email for assistance from Amazon USA. The parcel was returned in error by DHL and now they wash their hands. As a result of this, I am now past my due date for a refund and I still need to get the parcel back to the USA as I have no use for the item.