Why hasn't this hospital called me back?!

I applied for a volunteering position at Nemours Children's Hospital. They called me 3 months later in December and said they were having orientation in January. I went and was given an assignment in the Safety Store. They said the manager would call me with my start date. Two weeks later I still hadn't heard from them so I called the Volunteering Dept. The lady told me they had filled all the spots and had to put me somewhere else. Then she said the coodinator was sick and would call me when she came back in a few days. That was about three weeks ago and I have heard noting from them. Why did they waste my time and have me come to orientation and now saying I don't have a position. What should I do? Are they being racist (I'm African American). Shoul I apply at another hospital or pester them?