Have you tried hard to resolve this with the training provider? Not only is it fair to the FTO to try everything they are willing to satisfy your complaint but you are very unlikely to gain by legal action if not. If you have and still you feel unsatisfied then I suggest you try to contact someone who can give an independent opinion that what you have gone through is against normal industry practice etc. Obviously you have not given enough detail here for us to judge, and may not be able to, heeding Keygrip's warning!
If you still feel aggrieved, good luck.