Hi Khan,
I think The Configurable Material belongs to table MARC.
Please try the steps below which will allow you to deallocate the wrong Configurable Material
Go to table MARC
Put your material and plant
1 entry will be displayed.
Double click on it
you will go to detail display
Now put /H in command field
Hit enter twice
You will go to de-buging mode
double click on 'code'
Now Code= show
change it to Edit
press F8
you will get the entry in edit mode
Remove your Confg. material assignment.
Save.
Venkata.