If a Grant that is already partially paid out to a different Grantee it is not possible to change to a different grantee and retain the information on the grant for the original grantee.
When you do a Grantee change to a different Grantee id, you are changing the idcode for the entire Grant and Voucher. If this is all right, then a grantee change can be done.
The Payee name will stay the same as the name originally paid on the initial payments. Subsequent payments will use the new payee/grantee names.
Many organizations will choose to cancel the remaining portion of the grant and enter a new grant for the balance for the new grantee.