You can cancel your games up until 6 or 4 hours before the kick-off without being charged a credit. There is a 6 hour time period in London and Stockholm.

All other cities are 4 hours. Please review our policy below.
​https://intercom.help/fcurban/en/articles/6525388-what-s-the-game-s-cancellation-policy
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After the 4 or 6 hours hours before kick-off you still have to cancel but it will cost you a credit. (Make sure you won't get a NO SHOW)

by changing your RSVP Status to “not attending” in the games info. Go to <My Games> and cancel booking.