发霉bread

we bought bread two days ago from Wildoat, opened and gave some slices to my son yesterday morning. I found this bread is actually molded yesterday afternoon. We have kept it at 4 degree all the time. I went to the store for it and they only can return it to me and no one would like to say sorry at all. I asked to see their manager and I was told the manager was not available. So I left my phone No for the manager to call back. But no one call me back. What can I do? thanks