Lack of customer service

I went to exchage an item i bought, at Mr Prece Centurion Mall, i explained to the security that im there to exchange an item, the security guard at the door took the item and doesn't explain process of exchanging. I had to ask her what do i need to do she just said leave it here with me no explanation as to why i need to leave it there...lack of customer service is appalling, i get to the till she still had the item with her at the door the cashier had to go to the door abd collect the item.