Request to contact credit manager on past due account

Gentlemen: Our two firms have been doing business together for a long time. Perhaps that is why we cannot understand why you haven't responded to any of our reminders advising you that your account has fallen seriously behind. We are here to listen if you are experiencing a problem and we are most anxious to maintain the goodwill that we have shared for so many years. We will not even request your payment in this letter, but merely urge you to contact our credit manager. Let us hear from you soon.