If the passenger paid too little, tell them to click the “Make a new payment” link in the confirmation page. This allows them to make a new payment for the difference that is owed. For example, if the fare was £15, but they only paid £10, ask them to make a new payment for £5.
If the customer paid too much, get in touch with us via the “Send Feedback” option in your app. You can also ask the passenger to get in touch with us either via the link in their payment confirmation page, or by replying to their email receipt.