Writing a complaint letter can help make a company aware of their shortcomings and give you a resolution that you desire.
If the letter is being sent as a hard copy, then it should be in the proper business format, otherwise, if the letter is being emailed, it should have an appropriate subject line and proper grammar.
I am a long-time fan of [Product Name] and have been more than satisfied with your products over the years. I recently purchased a jar of [Product Name] peanut butter from my local [Name of Store], expecting the same great taste I've always enjoyed. However, the peanut butter turned out to be grainy and rancid, not at all like the smooth and slightly sweet product that I'm used to.
On, [Date and Time], I immediately called customer service to alert them to the problem and spoke with a representative named Janet. As I was explaining what was wrong and expressing my concern that other products from your company may have been affected. When I finished speaking, she told me in a rather impatient way that [Product Name] experience natural variations from jar to jar and there was nothing that could be done. I asked if I could speak to a supervisor, only to be told again that there was nothing the company could do. Janet disconnected the call before I could say anything else.
I'm disappointed that a company like [Company Name] would provide such substandard customer service. Enclosed please find a copy of the receipt for the peanut butter along with proof of purchase. I would appreciate a refund or replacement product by [Date] and hope that you will deal with this lapse in customer service accordingly.
If you need to contact me for any reason, you can reach me at 555-555-5555. Thank you for taking the time to hear my concerns.