How to write a formal letter?

Use correct grammar and appropriate sentences.

For example:

Dear Mr.Smith,

My wife bought a china cabinet from your company store in Vienna, Virginia. We had 2 young men, who did not speak good English, assemble our cabinet. They left a short while after. I was assembling items in the cabinet when I realized it was missing 10 nails and a light. I called your store and they did not pick up. I called in a few hours later. A person picked up and told me people would come and help me on Monday, March 8th at 12:00. No one came at 12, 1, 2, 3, or 4!

I called your store and asked why. They did not know and rescheduled it, for the next day at 3. No one showed up at 3, 4, 5, 6, or 7! I want someone to come or my money back. Thank you. My number is 777-888-9990.

Sincerely,

Mr. and Mrs.Harbor