On your Apple TV, go to Settings > Users & Accounts > Choose
the correct User ID > Subscriptions 
BET+.Select Cancel Subscription and Confirm the cancellation. If you need to change the User, you can do so by pressing down the AppleTV or Home button on your remote, and switch to the correct user.

To turn off the subscription through an iTunes on a computer, please goto Settings Accounts Subscriptions, and turn off Auto-Renewal.
Your BET+ subscription will be available until the expiration date listed on the device. If you do not see an expiration date, check your Internet connection or try checking your other Apple IDs or iOS devices before repeating the steps above. Be sure to finalize your request by confirming your cancellation.

To delete BET+ from your Apple TV:
Navigate to the Settings menu
Press General
Scroll down and press Manage Storage
Scroll to the BET+ app and press the little trash can icon on the right
Confirm your selection and you’re all done!

Please remember you can cancel your subscription at any time, but to avoid auto-renew charges, you must cancel at least 24 hours BEFORE the end of your free trial or current billing period.