In case if there is any unfair treatment occurred, a letter should be written to correct the situation which is know as letter of appeal. This letter will let you tell your side of story to the reader. You can mention all facts that will support your case.
While writing appeal letter mention about the fact and logic about the issue, rather than writing emotional statement. Give brief description about the issue.
Begin your letter by saying about yourself and the purpose of the letter.
Keep the first paragraph as concise and clear as possible so that the reader can immediately understand its urgency.
In next paragraph(s) let the reader know what happened and why are you asking for appeal and why it needs to be granted.
Mention about the time and date when particular event occurred.
To make your letter easy for reader to understand write in bullet points.
At the end summarize what you have to say. Include the contact details and where you can be reached. Close out the letter by thanking the reader for their time.