bad service

so my hubby has purchased a pack of diapers at the Chatsworth center spar as we where spending the weekend in Chatsworth - we then wanted to exchange this at the phoenix plaza branch as we where unhappy with the pampers diapers- upon arriving we waiting 15 minutes for assistance - the lady looked at the slip and refused to exchanged as this was not bought at there branch - i asked to speak to a manager and he insisted this is the rule - does not have any proof to show but this is just spar rules- he was rude did not want to explain i find this extremely hard to believe as i know we can exchange at any spar as he just did not want this credit at his store