You can make international roaming and overseas calls at anytime, you'll just need to top up with an out of plan add-on.
This won't apply when roaming in the EU though, as that's included in your bundle.
You'll be able to use 12GB of data with your base tariff each month when roaming in the EU. If you would like to use more than 12GB of data, you'll need to purchase a data add-on from your dashboard.
For more information about international rates, our Price Guide has got you covered.