$500 via Verizon e-gift card (sent w/in 8 wks). Activation of 4G LTE/5G phone on One Unlimited for iPhone (all lines on account req'd on plan), 5G Do More, 5G Play More or 5G Get More plans req'd. Device must remain active for 45 days. $500 charge back if service cancelled w/in 12 mos or eligibility req's are no longer met. See vzw.com/bring-your-own-device for details.
Typically Verizon will have you cancel your current pre-order and place a new order. They're not fond of making changing to an already placed order. You can call but I suspect that this will be what they advise you to do. Good luck.