What would you do if a pharmacist gave your baby the wrong mediation?

Walgreen's yesterday gave me a bag with my 3 month sons name on it and the medication inside looked like what he had been taking. I went to give it to him and something told me, in my gut, to check the internal label as well. I did and discovered the medication was for a different person, and it was a high dosage. My father-in-law who's a pharmacist told me it would have caused major trouble with my 3 month sons nervous system. I called Walgreen's and their manager doesn't seem to care... How should I handle this. I am very upset that they almost seriously injured my 3 month baby and they don't seem to care.