I think you should just get the refund mate. Seriously. You are lucky if you been offered refund. Im not saying you shouldnt complain receiving something you werent sold. But if they are willing to refund it - why not?  Testing item for 2 days and hashing with it seems reasonable. Not like they had it for 2 months. Has with it for 2 days to get your hashing time back you lost. Then return it for refund.