If you choose to upgrade to a longer Babbel subscription and already have a subscription with us, it will work the same way as changing a payment plan – the original subscription will be automatically cancelled and the time already paid for added on to the first payment period of the new subscription.
If you upgrade to a Babbel Live subscription, please see the process here.
If your original subscription was bought via the Apple App Store or the Google Play Store, it's very important that you cancel this to avoid any further charges.