How do I cancel a subscription to CBS All Access?

Actually, it is quite simple to delete CBS All Access Account. All you have to do is:

1. Log in to your account.
2. On the My Account page, locate Cancel My Subscription.
3. Click the button and confirm your decision.
4. Confirm it once more on the cancellation terms page
5. Tell CBS why you’re cancelling and confirm once again.

That's the most basic method. Although that solves it almost 90% of the time, it might not work for you. Refer the below links for alternative methods if that's the case.

https://www.tivocommunity.com/community/index.php?threads/cbs-all-access.545676/

https://www.techwhoop.com/cancel-cbs-all-access/

There are instructions on this page for managing and stopping iTunes auto-renewing subscriptions : View, change, or cancel your subscriptions - Apple Support