Hello! I need to write a letter of apology because I missed a mock interview appointment. I was asked to write a letter of apology but do not know what to say at the beginning and what to say at the end. Should they contact me for another one or what. Please help me!
You will need to have a go at writing it first yourself.
Post what you have written here, then we can help you.

how to write apology leter if you commited mistake and ask a person to as you are
Students: We have free audio pronunciation exercises.
Pretend you are talking to the person. What would you say? Write down what you would say to that person.
Hi Anon

You need to try to write the letter yourself first. Then we can offer suggestions for possible improvement.
hello i love this song i want to get the leter
Teachers: We supply a list of EFL job vacancies
Dear XX;

This letter is a medium to express my gratitude for the opportunity of a second interview round with your organization. (brief explanation as to why you missed interview, but don't overdo it). Please allow me to express my extreme gratitude for your continued time and attention in the midst of so many pressing tasks. I can be available xxx. (Unless you don't want the interview)
yeah you need to write it by yourself maybe we can review it after