Bad customer treatment

OnAir TV sold my partner a product but on false basis. When He got the decoder package, it was not what He was sold and promised. Upon this realization, He attempted to Cancel but was told He would have to pay R4000 which is the monthly installment *12 months. However the monthly installment *12 is not up to that amount, I fact it is half of that amount. Is this lawful? To sell a product with lies and then make it difficult for the customer to cancel? Is this even legal?