rude,abrupt and poor customer service

my father had bought a supplement from iron circuit in umhlanga after the salesman sandesh had said it will reduce blood pressure and sugar levels. after taking it once my dad's blood pressure and sugar levels sky rocketed and he fell ill. we had then phoned the co-owner of this business and she had agree'd to help us out. so we went back there and explained to him and wanted either a refund/exchange as we dont want something thats a risk to my dads health. sandesh was absolutely rude calling my father a sick man,insulting him and calling my father arrogant and when we proceeded to phone his partner he insulted us further saying we should use his phone cause maybe we have no money. furthermore he never gave us a chance to explain anything as he kept shouting over our voices and then claiming he had warned my dad about the risks when he never did. i have never experienced such rude behaviour from a business before,how does one expect to be successful & build a customer base with an attitude like that,with R300 gone down the drain the draini wish you all the bad luck sandesh and hope your ego subsides and you open your steroid pumped self to the policy of the customer is always right