Refund complain

In July this year,I bought items from SHEIN and paid customs tax at Buffalo logistics. The failed to deliver my goods saying that I didn't pay. I sent several emails with proof of payment but still. I made calls and they even ignored and blocked my calls. They ended up returning my goods back to SHEIN. SHEIN refunded me the whole amount of goods within a week. I called to complain and got a Refund form to complete and email it back to them. To my dismay,I'm still waiting and when I sent emails, they don't reply.