Shein.in - Refund not initiated yet

My order id is BKK*****. I had ordered * jeans on **th May. I expected it to be delivered till **nd May but I received on **th May. So I applied for return. My return Id is *******. Shein provides for two options one is self sending and the other one is pickup by an agent. I chose pickup by an agent. Every shopping app has the same policy that the pickup agent will verify and check the items at our doorstep and then only they'll further transfer it to the warehouse. After verification, it was transferred to the warehouse on **th May but I didn't receive any refund. So today I contacted the Shein customer care service. They are saying items are non-Shein so they'll not initiate the refund of the amount of Rs. **** which is a big amount for a person coming from a middle-class family. I enquired them that the items were checked by the agent then and there itself. Still, they haven't refunded. Please help me as soon as possible. This thing is not at all acceptable.