I have € 2 of calling credit left but I can't call/surf/text. What do I do?
Disable your 4G-connection and reboot your device to be able to use your remaining calling credit.
We always reserve 20 MB for your next data session. As long as you have a bundle, you don't notice this. When you surf using your calling credit, you might notice your remaining credit taken into reservation. You can circumvent this by no longer connecting with 4G. This can be done in the settings of your device.
Apple: Settings > Mobile data > Switch off 'Enable 4G'.
Android: Settings > More Settings > Mobile networks > Network mode > Select an option without 4G or LTE
Nokia (Windows Phone): Settings > Mobile networks > Highest connection speed > Select an option without 4G or LTE.
In some rare cases, a top-up might be needed. Don't worry: this doesn't mean the credit is lost, it will be added to your calling credit after your top-up.