I am unhappy

Cash Crusaders advertised the Xbox One for 3,5 when I get to the shops the amount was different. When I complained because I know I came there budgeted the 3,5 not the 4k that they wanted me to pay. I was told that they cannot reduce it as the one that was advertised sold out were as it is the same thing. Some one called me today but I confused Crusaders with Converters. It was Crusaders