Especially if you’re not familiar with roaming and using the internet while travelling, it’s a good idea to be aware of how much you’re using while away.
Some carriers will send you free data usage alerts via text message to ensure you never spend more than you expect. If not, on most devices, you can use the built-in data tracker. You can reset it when you arrive in your destination, and check it every so often to provide you a rough idea of how much you have used. If your smartphone doesn’t have a built-in data tracker, you might want to download a usage tracking app such as DataWiz (iOS, Android; free), My Data Manager (iOS, Android; free), or Data Usage (iOS; $0.99). With these apps, you can set your own data limits, and the app lets you know when you reach that limit – helping you avoid extra charges.
(Note: Built-in data trackers and third party apps for data consumption tracking should only be used as a guideline and not for billing purpose)