bad service after buying somethng without a expiry

Just went to Pick n Pay at Kemp-square to take back the a yogurt that I bought. It had no manufacturing date or expiry date and the lady that assisted me told me that all products had the dates and that it could have been removed by the handling of the product especially in storage. And the attitude I received from her was bad. When I asked why do they put brands on the shelves without the necessary details, she kept saying it was there and it was removed. So in other words am lying. With all of that its sad having such customer service and with the risk of having food poising, one can never bee safe of the quality of food pick and pay has to offer. Something needs to be done about this and soon before more people are exposed to such or end up having staled or outdated food which compromises the health of the consumers