In your cPanel, spamassassin is enabled and you are unable to see the “Disable spamassassin” button in your cPanel. If you need this button visible under your cPanel do the following:

Login as root in your WHM.

Here, on the left pane you will see an option “Exim configuration editor” click on that. Home »Service Configuration »Exim Configuration Manager.
And check it under tab >> Apache SpamAssassin™ Options
Apache SpamAssassin™: Forced Global ON [?] ==============> Turn this option OFF
Turn on Apache SpamAssassin™ for all accounts (i.e. with no option to disable).
Save it.

Now, relogin to your cPanel account and check for spamassassin – you will find the button “Disable spamassassin”