To cancel your Pro subscription, please open your Manychat account, head to Settings --> Billing and click the "Cancel Subscription" button. Please note that you need to finish all 3 steps to successfully cancel your Pro account.
After that, please confirm that you want to cancel your Pro subscription.
The last step - choose a reason for cancelation, give a short description and then click on Submit.
If you see this - it means that you've successfully canceled your Pro subscription.
Please keep in mind that the subscription won't cancel immediately. The status of your subscription will become "Pending cancelation", and the subscription will be canceled completely at the end of your billing period. Do not worry, you won't be charged for it again.
If you changed your mind, you can get back to Pro during the "Pending Cancellation" status. To do this, just click the green "Return to PRO" button seen in the screenshot above.
NOTE that you need to cancel your Pro subscription first if you want to permanently disable your bot.
Hope this helps!