Making mistakes or upsetting people is a fact of life. We are human beings and none of us are perfect. If you upset someone then the most sincere thing to do is apologize. If a face to face apology cannot happen then you should do an apology letter. If you need some apology letter templates look here:
. http://www.abusinessresource.com/Additional_Resources/Business_Letters_and_Forms/Apology_Letter/ and www.perfectapology.com/sample-apology-letter.html