I changed the prefix of the supplier order draft from DSOR to PO.

Than I changed the prefix again to DOP, because it should be the DRAFT PO

After that I wanted to change the supplier order prefix from SOR to PO, I get message that the PO is being used.

The problem is that old value that were changed are not deleted, but instead are kept in the system.

Is there any way to delete the old value?