This letter informs a company that you need a replacement for a defective product rather than a refund.
1234, Main Street
Boston, MA 02123
<Recipient Address Goes Here>
<time you purchased the product> I purchased <product purchased> from your company. Since that time I have found that it <description>. The <product purchased> is necessary for my <use for product> so rather than ask for a refund, I need a replacement as soon as possible.
<statement about enclosed receipt and/or product> Please send me a new <product purchased> as soon as you can to the indicated address. Thank you for your time and attention to this matter.
encl: <List of enclosed items goes here>