wipe your data, step by step.

Open Settings > Accounts, then remove all Google accounts so Factory Reset Protection is disabled.
Go to Settings > Security > Find My Device and turn it off.
Remove any screen locks (PIN, pattern, fingerprint) to speed up testing.
Navigate to Settings > System > Reset options, select Erase all data (factory reset) and confirm. Let the phone restart and complete setup.
Check the welcome screen shows no previous accounts before you power down and package the device.

Back up with iCloud or iTunes/Finder so you do not lose anything.
Open Settings > [Your Name] and choose Sign Out to disable iCloud and Find My.
Remove any eSIM or physical SIM and unpair Apple Watch if connected.
Go to Settings > General > Transfer or Reset iPhone, tap Erase All Content and Settings and follow the prompts.
Wait for the device to restart to the Hello screen - this confirms your data has been cleared and the phone is ready to send.