Final answer:
You write an order request letter for formal correspondence when other ordering methods aren't available or when previous communications were ignored, and when formal requests or instructions are needed.
Step-by-step explanation:
You would write an order request letter when telephone and website ordering are not available, when someone has not replied to an earlier e-mail, when you have ordered a product through a catalogue, or when you have to tell someone to do something. Writing a business letter is a formal means of communication often used when dealing with companies, politicians, and institutions. For example, if you want to inquire about a job opening or ask for a refund for a faulty product, a business letter conveys seriousness and professionalism. If the matter is complex or serious and cannot be handled concisely in a brief email or message, such as disputing a charge or changing a work schedule, then a business letter or a direct conversation is more appropriate.