You can control how much data eStories uses when streaming on mobile networks with your Android or other mobiledevices.
In settings you can adjust the following:
Download only over Wifi. When this is enabled you will be able to download a story to your devices only if you are connected to your wifi and your data won't be affected.
Allow Streaming Playback. Turn this off, and you will only be able to stream on the device while connected to WiFi.