If you close the account during the first 12 months American Express may, indeed, retract the bonus -and- it may reduce your chances of qualifying for a bonus on other American Express cards. Leave the account open until the annual fee actually appears on a statement. That will be after the end of the 12th month, then you can call, consider any retention offer, and close without fear of a clawback.
How can they retract the bonus miles when I have already used them for an upcoming trip? Can they really ask Delta to cancel a pay with miles ticket in order to get back their bonus miles?