Canceling depends on where you originally subscribed: Apple (iOS), Google Play (Android), or the Speechbolt website.
iOS (Apple App Store)
Open Settings
Tap your name
Tap Subscriptions
Tap Speechbolt
Tap Cancel Subscription (or Cancel Free Trial)
If you don’t see a Cancel button, the subscription is already canceled and won’t renew.
Android (Google Play)
Open the Google Play Store
Tap your profile icon (top right)
Tap Payments & subscriptions → Subscriptions
Select Speechbolt
Tap Cancel subscription and follow the prompts
Subscribed through the Speechbolt website
Log in to your Speechbolt account on the website
Go to Billing / Subscription
Click Cancel subscription and follow the prompts
Important: Canceling billing ≠ deactivating call routing
After canceling, you may also need to deactivate Speechbolt on your phone so calls stop routing through the service.
Also note: deleting the app does not cancel your subscription.