No, the phrase "paid in full" illustrates that the amount _is_ in dispute.
What you need is for the amount to be subject to dispute. See how the example they give of an invalid attempt to do this is a credit card bill, specifically because the amount of the claim is fully objective?
What you need is for the amount to be subject to dispute. See how the example they give of an invalid attempt to do this is a credit card bill, specifically because the amount of the claim is fully objective?
The cover letter doesn't add anything there.