I need to write a formal letter to a company to request a refund for a defective product. My response should contain at least 5 sentences. Highlight at least 2 sections in your answer with markdown, i.e. *highlighted section*. Include keywords *refund*, *defective*, *product*, *customer service*, *inconvenience* in the response. At the end of your response, please explicitly add a postscript starting with *P.P.S*.

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