Data is not free for most people, if you are one of those then this article might interest you. Being an Android user, tracking your data usage is fairly simple as we just have to visit the default app that records entire data activity and even resets every fixed date of the month when the billing cycle resets.
In case you are an iPhone user, then you know there is no way (as of writing this post) to determine the amount of data you have consumed in the past month when not on wifi and thus you end up paying more charges for the data overage. This was the same case with my friends in my shared plan.
Well, here is a simple solution for you. There is a free app called as My Data Manager that allows you to monitor and track your data usage in your iPhone.
Using this app you can, not even monitor the data remaining, the time remaining before the data resets but even get alerts if you are close to consume all of it.
So give it a try, either visit your app store to look for it or just visit the link below and never pay for the unnoticed data overage.