Log in at DisneyPlus.com in a computer or phone browser (not the app).
Select your Profile, then Account.
Select your Disney+ subscription under Subscription.
Select Cancel Subscription.
What happens
Charges stop
You keep access until the end of the current term (monthly, annual or promo period).
Instead
Monthly plans billed by Disney+ can pause instead (Account → your subscription → Pause Subscription). Some plans can't pause.
The catch
Cancelling doesn't delete your Disney+ or MyDisney account.
Bundles get tricky. If you had Hulu, ESPN or HBO Max before switching to a bundle, cancelling the bundle restarts your original subscription at its current price unless you cancel that too.
Signed up through a third party (phone carrier, app store, etc.)? Cancel with them.
Pausing Disney+ also pauses everything else in your bundle.