To deal with complaints from customers or people in your social circles, you should address and validate the complaints, and then take steps to either make the person feel heard or offer solutions to the problem.
Customer Complaint: “You don’t seem to care.”. Response: “I do care, and I am going to do what I can to make this right.”. This is the #1 customer complaint. Actions speak louder than words. If a customer catches a whiff of apathy, they will be offended. Right the ship by proving you are actively working to resolve their complaint.
A complaint letter has its own importance as it goes into the record of the company and the company knows your complaint is genuine. Be concise when writing the letter. Explain the problem. Include any product reference and the model number. Be reasonable and mention the solution you are looking forward to.