You can check all bonus information if you log in to your account and then click in “My bonuses“.
In that menu, you can verify which bonuses you have currently Available, Active or Ended.
Once you click on “Active“, you will be able to cancel the bonus by pressing in “Forfeit bonus“.
Please bear in mind that by cancelling your active bonus, you might lose your generated winnings if you have not wagered them completely. For more information on the general requirements of your bonus, check its terms and conditions in that same menu.