Unfortunately all sales go through the device's respective store (Android devices use the Google Play Store, Apple devices use the App Store). When you subscribe to an island, the purchase is processed by these companies and they send you an electronic receipt.
If you didn't mean to purchase a subscription or purchased the wrong subscription, go to this electronic receipt in your emails and click "Report a Problem." This will open up a menu that allows you to request a refund.
For Google Play users, you can also go to the Google Play store, select "Menu," "My Account," and then click on Hawaii Revealed to request a return.
With both of these options, the sooner you submit the refund request, the easier the process is. After you have the refund, just buy the island subscription you really wanted!