How does bonus data on auto top-up work?

Bonus data is applied to your account monthly after each successful auto top-up, so long as your account is in good standing and continues to meet the bonus data requirements. If the bank account or credit card provided cannot be charged or you are no longer registered for Allowance or Automatic-Allowance top-up, the bonus data will not be applied and will be automatically removed from your account. Any unused bonus data expires after 30 days.