Unprofessionalism

Yesterday my daughter bought covers from pick n pay greenstone hypermarket by mistake the was a cover that was added when she got to the tills so we went to refund them at edenvale pick n pay and i was told i could not get a rwfund because i bought them at greenstone which a hypermarket i could only exchange because they dont sell the same items and thats their 'policy ' , which is only known by them because its not on the slip for consumers to see and acknowledge my problem is if they dont sell the same items why are even taking the items to exchange and as a customer how in the world amni suppose to know the policy if its withheld