Conned but ABSA can not help

I sold someone a generators for R8500 that I posted on olx and he made a payment at ABSA on the 07 August 2018 to my Capitec Account and the money did not get in my account so when I go to ABSA to find out how the guy got hold of ABSA's business letter and *****ed me they said they can not help because I am not their client I must come with the guy whom I never met but he sent a pick up bakkie to come fetch the generator with this registration numbers YCK 455 GP so need help educating people about this kind of **** and answer from ABSA on how these guys con people using their name and the name of the client servive consultant was Thozama Mavuma from a Pretoria branch