ASSIGNMENT OF PLANT TO COMPANY CODE

I have performed following configuring steps for enterprise structure.

1.Defination

a.Create the company

b.Create the company code by copying from the standard SAP 1000

c.Create the plant by copying from the standard SAP 1000

2.Assignment

a.Assign the company code to company

b.Assign the plant to company code.But here the created plant is already assigned to 1000.This message is displayed in the plant assignment screen.

So please suggest to resolve the problem.