Expired yoghurt still on the display fridge

Some days back a friend sent me to buy some yoghurt for her at our Local Lyndhurst Spar. I got there, grabbed the flavour she wanted and proceeded to pay and take it with me to her. She ate the yoghurt with trust as she bought it at a trusted shop. The next morning she was very sick, had a runny tummy and was vomiting. We were asked what she ate the previous day at work and i remembered the yoghurt i had bought for her. we proceeded to the dustbin to look for that container only to find it had expired a month before purchase. We told the management of Spar about this and all they kept saying for days is that the owner of the shop must decide what to do. They need be careful as they are dealing with people's lives and don't really care about it, on many occassions we have alerted them of food with mold and we still suffer the same thing over and over again. Disappointing and scary