Problem in changing password of sa account.

Hello,

 I cant change my password of sa. I have tried with codes below

ALTER LOGIN [LOGIN_NAME] WITH DEFAULT_DATABASE=[master]
GO
USE [master]
GO
ALTER LOGIN [LOGIN_NAME] WITH PASSWORD=N’NewPassword’ MUST_CHANGE
GO

But this also don't worked. Are there any ideas to enable or change the password of 'sa' account.