Isabelle or not - The story of a teenage orphan

Begginning

I don't know who I am. I think I'm Isabelle. But once someone asked me 'Are you Isabelle or not?' I said I'm Not and they laughed and walked off. That was 7 years ago when I was 5. So now my name is Not. I guess Ina and Luna were babies when it happened so they don't remember my name. I was 3 so I can't remember my name.
What happened? Oh. I was hoping you wouldn't ask but here you go:
They tell me I was 3 and all I remember is walking through the park. I heard a bang and everything went black. I woke up in a hospital bed what seemed like a few seconds later but they tell me was weeks later. I was put into this place with colourful pictures on the walls and lots of other children with sad looking faces. I didn't have many friends since most of them laughed at me when I said I didn't know my name. I didn't even remember my parents. Their names, what they looked like. All I had left of them was a bracelet made of shells. But I made one friend. We had these little events where we sat down and some adult would come and take us on some games. After one of those events one of the adults that lead the place I was at came and led my friend out. I followed but the door was slammed in my face. I never saw her after that. After a few years I was taken to this other place with some older kids. I was about 5 then. We still had those events but we had to wear a tag with a few words on it . Mine said 
Name:Unknown
Age:5
A man asked me my name and I thought way back to the walking and the bangs and the black and the name that came into my head was Isabelle. So I said Isabelle. Then I said 'Wait no.' And the man said 'Is your name Isabelle or not?' But I didn't understand so I just said which one I wanted ' My name is Not.' I said proudly. He laughed then walked off , leaving my sat at the bench with the other children.