Change the "Opted Out for free Apple pencil" to accept offer

Assuming that you have placed an online order with Apple, the only method is to cancel your online order before the order changes status to preparing to ship - and place a fresh order.

Otherwise, if the order cannot be cancelled, you will need to wait until you receive the order - and then return the order to Apple for refund.

if it were me then I would reach out to them to try and get their take on it and your options

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