I have tried to follow up, they are ignoring me

Hi , buffalo logistics doesn't want to give me my refund back,I have tried to contact them but they are not picking up ,I did order clothes at shein , some of the clothes are big, some are small,I requested a return so that I can get my refund, they did came and collect the clothes ,but now the claim that they didn't come it's more than a week now,I have the contact number of the driver who came and pick up my clothes ***) please help me I need my refund