You may manually change this at any time in your Apple ID settings:
a. Device Settings-->iTunes & App Store
b. tap your Apple ID at the top
c. tap "View Apple ID"
d. tap "Subscriptions"
e. select God's Calming Promises (this will automatically be selected if it is your only subscription app)
f. at the bottom of the screen tap, "Cancel Subscription" to turn off an auto-renewing subscription.
This will prevent the subscription from billing you when it starts next period. Your current subscription will turn off at the end of the current subscription term.
Note: Uninstalling the app does not disable auto-renewing subscription settings. If you intend to turn off your auto-renewing subscription, then you will need to disable it in your Apple ID settings as described above.