Going over your monthly mobile data allowance can lead to bill shock as the cost of paying a pence per MB rate can dramatically increase your monthly bill. 

So what can you do to take control and manage your data usage?

1. Most Android phones allow you to set your own usage alerts and even bar data once you have hit your allowance. I think this is a super, simple and free service which we should all be using to prevent the potential of bill shock. It is as easy as a quick internet search for 'limit data usage' and your make and model of phone. This should provide you with a quick and easy guide to set up this android feature.
2. IPhone does not have the same useful data alert / bar that Android has. It does, however, provide an overview of data usage and which apps are crunching through your allowance, but this is a manual process and reliant on you to track your usage on a regular basis. One reason you may be chewing through your allowance, is due to Apple's 'WiFi assist', which determines how good your WiFi connection is and if it deems the signal to be poor it will automatically switch the connection from WiFi to cellular, therefore helping you to eat through your data with ease. However, there are Apple apps out there, such as DATA USAGE, which will help manage Iphone data usage at a fraction of the cost if you compare it to the cost of going over your monthly allowance by oBytes.
3. Increase your monthly data bundle - Yes, this comes at an increase to your monthly service charge cost, but it can be a lot cheaper than paying Out Of Bundle costs for breaking your data limit. Be aware that once you increase your data allowance you won't be able to drop back down to a smaller bundle whilst in contract

As our obsession with our smartphones increases, so does our data usage, which on average doubles every 15 months. Therefore, if you manage your data proactively you will ensure you will avoid a massive bill from your mobile provider.