Work center capacity category change

Hi

I am trying to change work center capacity category say A to B. I took the list of open order operations via IW37N giving filter for TECO, DLT,DLFL and CLSD.

I unchecked the "Indicator: Calculate capacity requirements" from all orders and saved.

Now added a new capacity category B in the work center and assigned the new category for scheduling.

Now when i try to delete the old capacity category A, system throws an error message " Capacity is still being used". I checked the list of orders etc, i have unchecked for every thing.

Can any one help to find out a solution for the same ? Share your ideas on how you changed the capacity category in work center. is there any another way to change capacity category.

- Pithan