Very poor service Pick n Pay centurion

I went into Pick n Pay crnturion mall, i had bought 2 bags of pampers nappies sealed,and wanted to exchange for smaller size. I was asssted by a lady manager i think who said because i did not have the receipt i could not exchange. She said se would show me the rules, which i then asked to see. Instead she brought a gentalman by the man of Paul no papers or rules who then told me that they do not exchange baby goods as people tamper with them ( which i understood) then he said only if you have a reciept. So how does that make sence. They will not take it or exchange it BUT only if there is a reciept. I then asked Paul if it was a pair of shoes would he exchange it, i got a ****ie remark saying we dont sell shoes. I dont feel i was given the right customer care and im shocked that you would accept the goods ( even if tampered with)if a receipt is given niether of them could give me a answer as to why. Poor service PICK N PAY centurion especially both Managers