After you create a trade-in with your new Pixel order, you can't change the information for your trade-in device even if you contact the Google Support team.
If you want to trade in a device with a different storage size from what you selected during the checkout process, proceed with your trade-in.
Important: Your trade-in refund may be different from your original estimated value.
You can’t trade in a device with a different manufacturer or model from what you selected during the checkout process. You can use that device for a future Google Store trade-in.