Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Defective product, no customer service

I purchased the AW722 headphones (shipped from Digital Media Research), and have not been able to get a single sound out of them. DMR falls back on a no-return policy for headphones, and Acoustic Research has essentially no customer service. Their FAQs are lousy, irrelevant, or linked to irrelevant pages. When you receive a return e-mail, it always contains essentially no info or asking you for the info already sent, and it offers a URL for followup. Trouble is, the URL links to a page asking for your username and password, and I have found no way to register in the Acoustic Research website. Altogether unsatisfactory experience, and I am astonished Amazon carries this [product, seller, and manufacturer.