To know how to end a session, you should refer to the way you started the session. Was the session started with:
An EV charge card? → In some cases, you need the card again to be able to stop the session. If you don't see the 'stop' button, try swiping the card again.
An App? → If the app does not react, try to close the app (e.g., double click and swipe up) completely and reopen it. You should now be able to end the session.
Directly on the charger? → Make sure you try to stop your own session and not your neighbour's session, as this maybe requires additional steps.
Still having issues? Contact the phone number visible on the charger.