Send a letter to the company -- e-mails rarely get read. For addresses (and names of company execs) go to hoovers.com.
Avoid customer service. Send your letter to the company's general counsel or CEO (letters trickle down in an organization but hardly ever trickle up).
Keep it short. Stick to one page and state what the problem is and what you hope the company will do. (Keep in mind they're more likely to give you a replacement than a refund.)
Be polite. Use profanity or threaten legal action and your letter will probably end up in the circular file.
Make and send copies of all receipts and correspondence. You'll need them to follow up with someone else if you don't get a response.