Often, the iOS app store or Google Play platform will do an authorization charge prior to the actual charge. For a brief period, two charges will show up on your statement. When you see multiple charges, one is usually just an "authorization" charge that is pending and hasn't actually been billed to you. Eventually, the authorization charge will be removed.
If you're seeing two charges, please check with your bank to see if both of them have actually posted to your account, or if one is simply an authorization charge.
In other cases, you may have accidentally subscribed more than once. This can happen if you signed up on two separate devices using different email addresses.
If this is the case, please contact our support team for assistance.