Price differance

I went to Sportsmans Warehouse to buy a pair of Asics running shoes wich was orderd as the didn't had his size in stock. On arrival we asked for Prospect who we delt with when the order was placed, he was day of wich was understandable as it was his day of. After a while another sales lady helped us, she had to run around to look for the box of tekkies eventualy she found it and of we went to the till, at the till the cashier rang up the tekkies and recieved the discount as per arrangement, as I look at the till slip when I got in the car I notice they charge me the wrong price as the price on the box and the price on the receipt differs, I went back to the shop to question it as I am sure im not the only customer that got caught with this. When I question it Zandile Matsemela said to me whats wrong you got your discount, the more I explain its not about the discount its about the fact that I paid a wrong price in the first place. I really don't understand why do I always have a problem when I go there, for once I just want to walk in the store get what I want in the size I need it, pay for it and walk out without a fight, hassel free.