Depends on the other parent, the baby could be A or B or O but can't be AB.
Hospitals might make mistakes - such as switching patient's samples. Hopefully they didn't switch your baby.
So I would double check before rush to conclusion and do something which you regret later on. A DNA test would be more accurate if you'd like to confirm.
No matter what, the child is innocent. Regardless, the child deserves a normal and happy life.