Shein refuses to intervene in their chosen service provider's lack of service

Shein refuses to intervene in a return process bthey crafted. It's been more than 2 weeks trying to return unwanted orders to Shein through Buffalo logistics. There is no where in Shein's return process where i as a customer has a "luxury' of choosing a courier company to come pick up clothes from my home to Shein. Yet Shein refuses to intervene when Buffalo logistics doesn't come and pick up its goods. I demand my money back then from Shein because the service provider they have chosen doesn't render the service