Buffalo logistics refuses to accept a letter from the bank confirming payment made in their account

My mom is an old lady who ordered things from Shein and they where delivered to Buffalo logistics and she was sent the payment method for her to redeem her parcels, unfortunately she made payment immediately but forgot to write in the reference number, but fortunately she was able to get a letter from her bank confirming payment made to the Buffalo logistics but with no luck they are still refusing to deliver her parcel. We tried calling them I call them every single day more than 20 times but with no luck, she is frustrated her parcel might go back to Shein wherelse she made the payment.