bought amplifier and find out it is damage

My father bought an amplifier at cash crusader at kempstar mall in kempton park on 21-02-2015 .On the 09-03-2015 I vukile his son open the box of an amplifier while testing it I find out it was damage . I pack it back in the box ask my father to take it back for an exchange item . The manager told my father these not exchange policy only repair policy after 7 days and reason why we bought this amplifier was for family function on the 15-03-2015 .I ask the manager MR Mzikona who was not interested to listen to me .I then call head office on *** spoke to sandi ,she listen to my storey and escalet the massege to Mr Kobus ,he call me I then explain it again to him .he then escalet to the owner . I receive a call from christo ,he escaleted the call to Benedit . I am still waiting for respond now . Please assist me how to resolve this matter . Now 18:30 no answer from any one from head office . No sure to hire amplifier for the weekend .