Address customer complaints professionally with our acknowledgment of customer complaint letter template. Create and download a letter for free!The process of investigation is. An acknowledgment is one of the most common types of notarial acts, but it often confuses Notaries. Here are 5 steps to performing an acknowledgment. Describe your complaint in detail, attaching additional pages if necessary. Fill out this form completely. If your complaint was received orally, the acknowledgement letter will include a complaint form. You can complete the complaint form and return it to us. If you have already received an acknowledgment letter, include a copy of that letter.