One can easily cancel the subscription in app, by going to "Dashboard" >> "Pro Features" >> ''Cancel"
OR
One can cancel the subscription by following the below steps :
Open the Google Play app .
At the top right, tap the "Profile icon".
Go to "Payments & Subscriptions".
Select the subscription or prepaid plan you want to cancel for the TimelyBills app.
Tap "Cancel" subscription.
Follow the instructions provided by the Google Play Store.