The Oyster card system is brilliant but not perfect. Using the TFL website to manage your Oyster account will show any problems with overcharging and arranging refunds. Setting up an auto top-up means you never have to top up due to “seek assistance” messages on the barriers. Visit the official TFL Oyster website, where you can sign up for an online account or log in to an existing one.
Due to various ticket barrier issues, it is common to be charged the daily maximum when a journey is not “touched in” and “touched out” correctly. Using the TFL Oyster Website will allow you to see if this has happened and resolve the problem. Unfortunately, it is still time-consuming to complain about being overcharged. TFL staff seem to have the attitude they are doing you a favour by giving you a refund. There is a facility to get a weekly travel statement emailed to you. The report is handy as most of us have better things than continually checking the website. Overcharging events will appear on the statement, but there is a time limit for refunds.
There is a mobile App which allows users to manage their account on the go. The App makes users more likely to manage their accounts actively.
No doubt TFL make a considerable amount of money from accidentally charging additional journeys and probably don’t want to lose that revenue. At least they have given us some tools to see when it happens and get a refund.