What to do when mobile charger is not working properly | Replacement of charger or buying the new one?

The charger given with the phone by the company is not working properly, as there is a warranty of one year, it was given for replacement.  But the same charger was given to the customer, saying that it is the new one.  The company is not paying any attention.  What is to be done in such situation?   Buying a charger which suits to the mobile phone is a simple solution.  Even if some money is spent there would be no mental tension.  But if there is a feeling that this is cheating, make a complaint to the consumer forum.  But it is to be proved that the same charger which is not working is given to the customer at the time of replacement.  If the customer is confident of proving it he can go ahead with the complaint.