Buffalo making the process for a refund almost impossible

Absolutely terrible service. My Shein order was lost, and I requested a refund. Shein refunded me immediately, but Buffalo logistics is making the process to get my refund almost impossible. They ask for proof of payment, I've send them my bank statement where it shows the payment, and they are refusing this statement as proof of payment. They want it in a specific format, but they never stated this from the start. This process is so unpleasant and I am sad to say that I don't think I will order anything from Shein again due to the poor service from Buffalo.