Your reader doesn t want to hear your entire life story. Drive home your facts. Give dates, times, and names of the people involved in your situation. If it took an hour to get through a checkout line at 8 AM it sounds much worse than if it took an hour to get through a checkout line at 8 PM on Christmas Eve. Also, this lets your reader know that you are a very organized and professional person.
Professional customers get better treatment in most cases.
Don t embellish. If you had to wait for an hour, don t say that you spent your entire afternoon waiting. As long as you stick with the facts of your story, your reader will be more likely to believe your writing and therefore be more willing to help you out. Generally requests fall into four main categories. First is the request for a refund.