Pretermination rate

Ad Majorem.....Wealth Builders

Somebody asked me to sign the interest payment for a matured PN.  The check was for PHP 9,000.  The note matured on December 7, 2012.  However, the owner of the note had a prepayment of PHP 50,000.  So as per the PN, there was a pretermination and that calls for just 50% of interest payment.  And the interest payment just have to be PHP4,500.00, not PHP 9,000.