If you have performed incorrect billing you can fix this in Medilink.
You need to work backward essentially.
Firstly consider if the billing has already been claimed or sent in some fashion.
For instance a same day delete may need to be done for patient claims.
Or for bulk bill or DVA or IMCs you may need to contact Medicare/DVA/Funds in some way.
If it's just been sent as an email or paper based receipt/invoice you should contact the party immediately and say that you will send updated documents as soon as possible.
Then you continue to work backwards in the form of the Appointment -> Invoice -> Payment screen - undoing and payment that was done for the invalid billing.
Then the Invoice billing itself, i.e. fix the items and description.
If it was for a completely different patient you may also consider removing the Appointment altogether.