Your option to disable the security pattern, PIN, and password may sometimes be grayed-out, and you may experience this issue if your phone is set up in any of the following ways:

1. See if you are connected to a Microsoft Exchange server that forces a screen lock.
   In this case, you will not be able to disable the screen lock without removing the Microsoft Exchange account.
   
   
2. Check if your device storage has been encrypted.
   Once encrypted, your phone requires a screen lock. The only way to remove this is by performing a factory data reset. See How to factory reset a device.

If neither of the above configurations are present, you may be able to disable the pattern, PIN and/or password lock on your phone by performing a Clear all Credentials option under Settings > Security.