Rules on Civil Procedure
Section 7. Substituted service. - If, for justifiable causes, the defendant cannot be served within a reasonable time as provided in the preceding section, service may be effected (a) by leaving copies of the summons at the defendant's residence with some person of suitable age and discretion then residing therein, or (b) by leaving the copies at defendant's office or regular place of business with some competent person in charge thereof. (8a)