Make sure you write a formal business letter. You should start out with an inside address (your address), then the address of the business, then the date, then a salutation (the name of the person that you will be sending the letter to or the phrase (To whom it may concern) followed by a colon ( : ), then your request (it would be a good idea to have examples and reasons why you want the shop rental reduced), then the word Sincerely followed by a coma, four returns then your name. Make sure you sign it before you send it.