271. If any rule provided in sections 25 to 28 governing the making of contracts is not observed or if a contract does not conform to the requirements of this Act or the regulations, the consumer may demand the nullity of the contract.
In the case of a contract of credit, if any of the terms and conditions of payment, or the computation or any indication of the credit charges or the credit rate does not conform to this Act or the regulations, the consumer may at his option demand the nullity of the contract or demand that the credit charges be cancelled and that any part of them already paid be restored.
The court shall grant the demand of the consumer unless the merchant shows that the consumer suffered no prejudice from the fact that one of the above mentioned rules or requirements was not respected.