OBC Take Out bad service

I went to OBC Take-out-real-good-food in Tembisa plaza and the food had a paper in it, and when I told them about the paper they took out the paper and brought back the food and told me that it's not their fault that the food had paper in it. I called the manager and she told me that it's not her fault and there is nothing she can do about it. In situations like these what do we as customers have to do.