I'm being forced to pay for something I did not request

The pathetic service I received from from this horrible store on the 27th of February. on the 25th of February I went to an mtn store to apply for a contract I was very specific that I wanted an iPhone with a bigger screen the gentleman that assisted me did not have a demo to show me and when he opened the device I was given an iPhone 8 with a smaller screen the screen is much more smaller then my current phone . When I spoke to him he told me there is nothing he can do. Which is rather shocking he brought his manager who also confirmed the same thing which was 'there is nothing he can do' so that means now I have to pay for something I'm not happy with better yet still which not my fault I'm disgusted the the manner of which this was handled and according to CPA I have the right to exchange the device if I'm not happy provided I was not even shown the device or I'm getting treated like this because I'm black assumed that I do not know my rights ? IM TAKING THIS TO CONSUMER COUNSEL and this will not be the end.