Poor after-sales service

Very efficient in collecting the faulty inverter I bought,only to reject my claim: "this is not the product you bought from us".???? I checked my order and noticed that I received the cheaper product (but paid for the more expensive one).They are almost identical,just a very small a different make.They sent it back to me. I sent it back again,logging another complaint that they sent me the wrong product from the start.Again my claim was rejected: "Refer to our 30 day return policy.If you are not satisfied with the product,you need to send it back within 30 days"