Pedro Reyes, acting as "President" of Sigla Traders Corporation (STC), entered into a contract to purchase PHP 4.5 million worth of construction materials from Liwayway Suppliers, Inc. (LSI). In the contract, Pedro represented that STC was "duly organized and existing under Philippine law." When STC defaulted on the outstanding balance of PHP 2.8 million despite repeated demands, LSI filed a collection suit against Pedro personally. In his defense, Pedro argued that he cannot be held personally liable because he merely acted as an authorized agent of STC, which has a separate juridical personality distinct from its officers, and that the doctrine of corporation by estoppel bars LSI from now denying the corporate existence of STC given that LSI had contracted and dealt with it as a corporation. LSI responded that STC was never registered with the Securities and Exchange Commission. Is Pedro personally liable for the PHP 2.8 million unpaid obligation? Decide with reason(s). (Bar 2026 Syllabus)