Apple needs to be clear the difference here.
turning off Auto-renew does not "immediately" cancel anything, since its still active and will stay till the billing date, tne it will cease..
Furthermore, "turning off" suggests your subscription would be cancelled. this is now how it works with Apple, it just doesn't renew, and by Apple's definition, by not renewing, it's effectively cancelling... (only because u cannot choose to pay month to month.)
I dunno why Apple associates auto-rewel option with "cancellation" of ones subscription, or all other services like hulu that u can use ITunes billing to pay for, because it just turns off auto renewal but it's only Apple that treats it this way.. No other company does.
Cancellation and turning off auto-renew are actually two different thing, although they accomplish basically the same.
I found no disable button as mentioned previous, but i did find this