Midas sasol circle near foresthill centurion

Last year march l went to midas to buy a battery for my car , they tested the alternator and wverything was fine . Today l try to return the battery because of late its been giving me problems . The lady at the back of the salesman said there was a problem with the alternator therefore no refund or warranty , l then asked to have someone check the alternator for me only to find out the alternator is ok . When l got back inside the lady told Sydney the salesman not to chamge the battery for me despite the alternator test proved everything was ok