You can top-up your credit directly from the app with an in-app purchase or sign in your account at our home page . The packages are 9.99, 19.99, 29.99, 49.99 EUR. The exact amount which will be debited depends on the currently exchange rate at Roamer or the payment system (Appstore, etc.) where applicable.
The rates and billing are done in Euro. In settings you can change the currency in which your balance with Roamer is displayed.