Given wrong parcels

I sent my mum to buy some stuff at Pick n Pay Evaton Plaza today, and she left her other items at the kiosk (where you leave your parcels) she bought the staff at Cambrige and when she went to fetch her parcels they gave her the wrong ones and she only realised when she got home, she called them they said she must come back to the store they will check their cameras and help.she went back and she has to use a taxi to get there, when she got there and confirmed that she was given the wrong parcel and she showed them the slip of the items,then the manager says she must buy items of that amount and they will refund her she doesnt have that money on her and whats going to happen to the kids as she bought food for their lunch box, so my mother must be inconvenienced and the kids because of your staff incompetence? I feel it is poor service they can prove that she was given wrong parcels why not let take whatever she bought at their store since it is their fault. you assistance will be highly apprciated ********** 635