We've noticed that some merchants will do a test/pending charge, before actually issuing the charge, as a way to ensure there are funds to cover the expense. These usually go away in a day or two although they might still show up after you cancel your subscription.
If after a couple of days, you still see that charge on your card, please let us know. The steps below will explain how to access this information, so that we're able to isolate the charge on your behalf.
1. Navigate to https://payments.google.com/payments/home
2. Login with the google account used to create your subscription. This will probably be the address tied to your Android devices.
3. Locate the Boomerang monthly subscription
4. Select Manage
5. Select View Transactions