Don't worry. Your payment is fully secured. When a guest initiates a booking request, the booking amount is only pre-authorized (not charged).
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This is NOT a charge. It is just a pre-authorization (similar to when you check in to a hotel). If the booking gets accepted, then this becomes a charge. If it is not accepted, then it gets reversed. This pre-authorization is done to ensure that the guest has money in the account to pay for the rental.