It is not possible to change a Part Code on the system.
The only option would be to create a new Part Code, with the correct Code
On the old Part Code set the Active Status to Superceded
In the Superceded By you need to enter the new Part Code
If there is any stock on the old Part Code that needs to be moved to the new Part Code, this can be done by the following steps
On the old Part Code go to the Transfer Tab
Complete the values for the relevant From and To
Right Mouse Click and select Transfer Lot to new part
The system will then validate that the groups settings are the same on the part code you are transferring from/to
Then Apply to save changes