D- South Society,
6 January 2012
<Mention recipient’s address>
Dear <Recipient’s name>
This is to inform you that we have received your payment of <amount> on invoice number <invoice number>. Because <specify reason for underpayment>, you still show a balance owed of <amount> to us.
<Specify the action taken>
For any queries, please feel free to call us at <phone number>. We would appreciate your prompt attention to this matter.
encl: <mention list of enclosed items>