Hi again,
Since it's a public computer, the system likely has admin restrictions that's why you can’t remove or switch the account. Please try to sign out completely. Clear saved login info via Windows + R > type control keymgr.dll > remove saved credentials if allowed. If you signed in through a browser, log out there too and clear cookies. Change your Microsoft password afterward to sign out of all sessions just in case. This helps protect your account even if it still shows on that device.
Warm regards,
Cherrelyn