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2. Join all the WiFi networks!

Now we get to the most practical – if slightly risky – piece of advice. Modern smartphones have two data receivers: one for mobile networks (3G or 4G), and one for WiFi. As in, the same system your notebook PC uses to connect to your home router.

Your phone can connect to a wireless network and get its data just the same as your main computer. So when you’re at home, it stands to reason that you should have your phone set to pick up the house WiFi.

The good news is that today’s smartphones are indeed smart enough to know that if there’s a WiFi network nearby, the phone should get all its data off that network, and not use the mobile data network at all.

Don’t just use the home WiFi, either. If you’re lucky, you can leapfrog from WiFi to WiFi all the way in to work and back. Some networks are open, so watch out for security (maybe don’t do your internet banking at the coffee shop).

The risk we mentioned comes in the way that, if the WiFi network shuts down or you move unintentionally out of range, the phone will switch automatically back to the mobile network. Boom – you’re spending again.

1. Set hard data limits!

At the end of the day, a crazy data bill is caused by the fact that it’s really hard to tell how much data you actually use on your mobile. How big is website X? Was that video I just watched HD or SD? What’s the bitrate of this streaming comedy radio network? Is this trailwalker app getting these maps from online or are they preloaded? Aaagh!

 

Many Android phones can alert you to when you're approaching your data limit.

 

Android-4.0-based smartphones now have a built-in data usage monitor, and other phones have apps that do the same thing. The great thing about this monitor is that you can set it to first warn you as you approach your data limit, and then you can set it to disable mobile data once the actual limit is reached.

What’s more, the phone will give you a breakdown of which apps, features and services are using data, so you can better adjust your own usage. Most of your data coming from app updates? Turn off updates!

Of course, your phone measures data in one way, and your mobile network provider might measure it in a different way. So it’s usually a good idea to set the data limits slightly below what it says on your contract: 50–100MB should keep you safe.