1. In the sample letter, fill in your personal information. I respectfully request that your offices provide me with competent evidence that I have any legal obligation to pay you.For example, the letter should contain their full name, contact information, and a clear explanation of what information they are disputing. Our guide will teach you how to write a letter of explanation, plus offers a free template to help you write one of your own. Here's how to write a debt validation letter: 1. See a sample credit dispute letter below.