How do you downgrade your IOS without a computer?

So! I hate the new update abd just would like to know if I can (without having to use a computer would be ideal because mine has seemed to lose its charger haha) downgrade back to the previous IOS system?! My iPhone somehow lost its hotspot with this last upgrade 14.2, and is just all around being slow and laggy and just “off” I want nothing more then to just go back to the old IOS!! Please help?!