How to disable the passcode when my phone is locked on Iphone5 ios 7?

My mom has the Iphone 5 and I updated it to ios 7 but she used to have the option of pass-code disabled and now we don't know how to do that again. It doesn't seem an option.

If you don't know passcode you can't do anything.
You can only restore to factory default setings.
This tutorial might help you
http://ihash.eu/how-to-put-an-iphone-into-recovery-mode/

Settings > General > Passcode Lock > Enter passcode > Turn Passcode Off (it is the first selection) > follow the rest of the directions