After PO Can i able to change the material code in PR

Hi,

I need a small clarification.

I created one  PR  then with reference to the pr I posted One PO. Fine,

Now i delete the row at Po. and then I cancel the release of PR through the ME54N.

If I Cancel the PR Release, then Qty field at PR will be enabled i can able to change it.

But Material code i am not able to change it. May i know is there any possibility to change it.

Qty is still showing in OPen qty. How much i raised. Through the ME5A i checked it.

But Material code i am not able to change it at Purchase Requisition.

Is there any possibility please update me.