Bad customer experience

I bought a phone 4 days ago and on my way home I see the packaging says 2800 but I bought it for 3000, so today I go to Jet stores in Canal walk century city, a cashier calls a guy not sure if he is a manager or what, he tells me 2800 is the price they bought the phone with, like really? So how is that my problem and why must I belive that that is true, cos I think I was ****** a 200, ****** wasted my time going there after a long day at work