Yes, you can update this in both Xero and MYOB. You need to remove the payment, edit the transaction and reapply the payment.
In Xero:
- Go into the payment transaction, Select remove and redo from the options menu on the right side
- From the bill options, click edit to make a change and select update
- Reapply payment
In MYOB:
- Locate the payment transaction and from the edit menu, click delete payment
- Edit the transaction, make the change and reapply the payment