Bought a Phone Without the Passcode—Can It Be Reset?

You can connect the phone to a computer and use recovery mode to erase it, but that only removes the screen passcode. If Activation Lock is enabled, setup will still require the previous owner’s Apple Account credentials, and there’s no legitimate way around that. Without the seller removing the device from their account, it’s effectively unusable.

The exact model and software version would determine the recovery-mode steps, but neither affects Activation Lock. Only the person whose account is linked to the phone can remove that lock through the proper account settings.

A passcode-locked phone may also be lost or stolen, so it’s best not to try to bypass the security. Since the seller refunded you, return the phone or check with the manufacturer or carrier about whether it can be identified and properly released.