Shein failure to provide customer service

I have been trying to get hold of someone of Shein to let them know they have to check up on the courier companies they use as Buffalo logistics failed to pick up the parcel I wanted to return and now I can not return it at all. It is clear on the site that I placed my return before the expiry date and now neither Buffalo logistics nor Shein wants to take responsibility and now I sit with a financial loss. This is unacceptable and it needs to be resolved. Due to this service I will not recommend Shein to anyone.