The promissory note presented by petitioner cannot be considered as adequate evidence to show the excessive placement fee. It must be emphasized that a promissory note is a solemn acknowledgment of a debt and a formal commitment to repay it on the date and under the conditions agreed upon by the borrower and the lender. A person who signs such an instrument is bound to honor it as a legitimate obligation duly assumed by him through the signature he affixes thereto as a token of his good faith.[18]
http://sc.judiciary.gov.ph/jurisprudence/2011/february2011/179242.htm
Batas Pinoy 