Was your instructor a regestered ADI displaying a green certificate in the windscreen when he was giving tuition or a pink badge for a PDI?
If not contact the police as they are commiting an offence by giving paid tuition.
If they are registered ADI's or PDI's the DSA 's concern is only with their standards of tuition.
They do not deal with instructors buisness activities. If you feel your instructor has obtained money from you fraudently go to the small claims court to seek recompense.
If you are successful then the DSA may take action against the instructor if you can then prove your instructor is not " a fit and proper person " to hold an ADI licence.