If before or during the preliminary hearing of any person arrested pursuant to a warrant, or appearing in response to a summons or citation, it appears that the complaint does not properly name or describe the defendant, or the offense with which the defendant is charged, or that although not guilty of the offense specified in the complaint, there is probable cause to believe that the defendant is guilty of some other offense, the judge shall not discharge or dismiss the defendant but shall permit the attorney for the Commonwealth to amend the complaint if substantial rights of the defendant are not prejudiced.