ZARA needs to be more entuned with their customers

I made two separate purchases one at ZARA Mall@Africa ( 2 x shirts at R799) and ZARA Menlyn (1 x shirt at R799 and a1 x tie at R600). I had the slip of the Menyn but misplaced the slip for Mall2 Africa. All I needed is to exchange ONE shirt because of size. Note the shirt is in the original package and with all and has all the tags intact. I am loyal customer to ZARA for more than 10 yrs even before ZARA opened in SA. I had mislaid the slip but have proof the card transaction at Mall of Africa. I asked that ZARA assists with an exchange. but they said they cannot help because I did not have the slip. This rule is so old fashioned (excuse the pun) for a progressive company Like ZARA, you have to be adaptable to the current customer way of life and you should think out of the box. We are living in a technology-centric environment and I shop so frequently at ZARA so you saying I must keep all my paper receipts because your product development and executive management at ZARA are not creative enough to think of making a customer's life more convenient. I can come up with so many ideas and processes while having breakfast that will resolve these issues and make you ahead of your competitors, why can't you. Please can I talk to someone at customer service? So I can understand what would be the purpose of the HARD COPY if have all the proof that I purchased it from your store and that the product is in perfect condition. I know it is just one shirt, but it is more about the principle of the matter, I am not even asking for my money back, it is just an exchange. Thank you and kind regards Colin