Because Google manages all subscription purchased through the Google Play Store, you'll need to follow these instructions on your Android device in order to cancel your free trial:
Open the Google Play store app
Check to make sure you're signed in to the correct Google Account
Tap the menu in the upper right-hand corner (looks like a hamburger icon)
Tap your Dipsea subscription - if you do not see Dipsea listed here, then you have not activated a Dipsea subscription or free trial
If it has been canceled, you will see the expiration date listed. If it has not been canceled yet, you'll see the renewal date, along with the price you'll be charged at and an option to cancel.
If you run into any trouble, this Google Play help article includes additional details for canceling your subscription.
Note: A free trial must be canceled before the trial's end in order to avoid a charge from Apple (iPhone) or Google (Android). If you've been charged and would like to request a refund, you can find instructions for requesting a refund from Apple here and from Google here
To learn how to cancel a free trial on an iOS device, click here.