Cannot delete reservations

Hi

I have a number of reservations and when I try to delete them (transaction MB22) I get the error message:

"Reservation created automatically. No manual changes possible"

Now, how can I delete this reservation? It is from the year 2005 so it just has to be deleted.

I am trying to find the material document for this reservation, but when I go into transaction MB23 and then "Environment"->"Materials document for material" there is no matching material document....so does anyone know how I can find the material docuemnt for a reservation? Or how I just can delete the reservation?

Thanks

Ola