When the Controller has determined the fair rate of charges in respect of a hotel or lodging house,--

   (a)  the manager of the hotel or the owner of the lodging house, as the case may be, shall not charge any amount in excess of the fair rate and shall not, except with the previous written permission of the Controller, withdraw from the lodger any concession or service allowed at the time when the Controller determined the fair rate;

   (b)  any agreement for the payment of any charges in excess of such fair rate shall be void in respect of such excess and shall be construed as if it were an agreement for payment of the said fair rate;

   (c)  any sum paid by a lodger in excess of the fair rate shall be recoverable by him at any time within a period of six months from the date of the payment from the manager of the hotel or the owner of the lodging house or his legal representatives and may, without prejudice to any other mode of recovery, be deducted by such lodger from any amount payable by him to such manager or owner.