Return of late payment and denial of discount

Your check in the amount of $ [dollar amount] is being
returned to you because it has been made out for the wrong
amount. As we have explained previously, the [%]% discount
we offer can only be applied when your payment is mailed
within 10 days of delivery. By waiting beyond that period,
you forego the opportunity to deduct the discount from the
amount of your invoice. Since your payment of the above referenced invoice was not
made within the specified time period, you are not entitled to
a discount on this order. We appreciate your business and
are most willing to accommodate you in any way possible.
Our policy, however, in regard to open account terms, is
strict, and in fairness to all of our customers, must be even
handed. Please remit your check for the full amount of the invoice.
Your cooperation in this matter is appreciated. Thank you
for understanding. Very truly yours,