Dear

A review of your loan account indicates that you have
had three checks returned unpaid from your bank.

While we regret having to take this action, we must
insist that all future payments on your loan be made
with certified funds. Any payment which is not
certified will not be accepted and will be returned to
you, possibly causing you to incur a late charge.

In making all future payments, please send them to the
attention of [denote] for proper credit.

Your cooperation is appreciated.