If you want to stream songs or watch lots of video on the go, you'll probably want to have unlimited data - or at least a generous data allowance. But does 'unlimited' really mean you can munch as many megabytes as you like?
Each of the main mobile networks in the UK - Three, Vodafone, O2 and EE, which also runs Orange and T-Mobile - has its own approach to data. Some plans clearly state a set download allowance, while others described as 'unlimited' may still carry a fair usage policy.
When choosing a mobile network, it's a good idea to look at the terms and conditions, as some deals will suit your needs better than others.
A summary of each mobile network's data policy can be found below.
Three (www.three.co.uk) prides itself on offering all-you-can-eat data. It provides "genuinely unlimited" mobile internet use with no danger of bill shock, which you may get with restricted data plans. It doesn't separate 3G and 4G - sign up to a Three all-you-can-eat data plan and you'll get 4G - so long as you're in an area of covered by Three 4G and have a 4G-compatible phone of course!
EE (www.ee.co.uk) 4G plans come with varying data limits, but none of them are unlimited. Plans range from 500MB of data a month to a massive 20GB of data a month. EE will let you know if you're close to hitting your limit, and if you are you can buy a data add-on to get more.
EE doesn't offer 3G directly, but you can get 3G with unlimited data from T-Mobile, which EE operates.
T-Mobile (www.ee.co.uk) offers 3G plans with unlimited data and no fair usage policy. That means that you can browse, download and stream to your heart's content on 3G at least - you can't get 4G plans with unlimited data from T-Mobile or its parent company, EE.
If you pick a Vodafone (www.vodafone.co.uk) 3G or 4G plan, a set data allowance - anywhere between 250MB and 20GB - will be stated in the contract. You can then check what you're using via the MyAccount page on Vodafone's website.
One cool thing about Vodafone is its Data Test Drive, which is available to new and upgrading pay-monthly customers. It allows you to use as much data as you like - with no restrictions - for the first three months of your contract. After that, you can upgrade or downgrade to a data bundle that suits your actual usage.
O2 (www.o2.co.uk) doesn't offer 3G or 4G plans with unlimited data. Its plans range from 100MB to a fairly generous 8GB a month. There's not much chance of you accidentally going over your limit as O2 lets you know If you're getting close to it and, if necessary, you can purchase top ups to get more data.
giffgaff does things a little differently to most networks. It's online-only, its community provides technical support and it phones are paid for through peer-to-peer lending, meaning the more you pay up front, the less you pay each month. With giffgaff you pick a 'goodybag' of calls, texts and data, one of which includes 3G with unlimited data. It doesn't offer 4G goodybags with unlimited data.
Goodybags are pay-monthly, but there's no minimum contract term - if you find you don't actually need unlimited data you can switch to a cheaper limited data plan the next month.
The whole talkmobile thing is low-cost plans, so as you might expect, it doesn't offer 3G plans with unlimited data, or offer 4G plans at all.
if affordability's your thing, it's definitely one to look at, but if you have your heart set on unlimited data, it isn't the network for you - its plans only go up to 2GB of data a month.
Virgin Mobile (store.virginmedia.com/virgin-media-mobile) offers a 3G plan with unlimited data. It's one of its new Freestyle tariffs, which let you change the amount of call minutes, texts and data you pay for each month, depending on what you need. It's flexible, but still rewards commitment - the longer you have the plan, the cheaper it gets.
You'll also pay less for an unlimited data plan if you're a Virgin Media (www.virginmedia.com) broadband or TV customer.
Virgin Mobile doesn't offer 4G yet.
Much like Three, if you have a 4G-compatible phone, Tesco Mobile gives you 4G at no extra cost. Unfortunately, none of its 4G plans are unlimited.
The maximum data allowance available is 8GB a month - that's generous enough to do a fair bit, and you'll be warned if you're nearing your limit, but if you're set the peace of mind you get with unlimited data, look elsewhere.
Mobile by Sainsbury's
Mobile by Sainsbury's is all about affordable sim-only plans and good value 30-day call, text and data bundles. As you'd expect, none of them offer unlimited data, with the top plan coming with 2GB a month. Mobile by Sainsbury's doesn't offer 4G.
The People's Operator
The People's Operator, or TPO to its chums, does pay-monthly and pay-as-you-go sim-only plans with some of what you spend on them going to a charity of your choice. It doesn't offer 3G plans with unlimited data or any 4G plans at all. Its top-end plans give you 3GB of data a month.
However, it has offered 3G with unlimited data before as a special deal, so if the idea of a more socially-conscious network appeals, check to see if any such deals are currently running.
What is mobile data?
In the same way that mobile networks charge you to make calls - or include a certain number of minutes with a pay-monthly plan - there are costs involved with connecting to the internet on your phone.
Whenever you send an email, check Facebook or download an app, your phone is transferring data using your mobile network (unless you're connected to Wi-Fi).
To help keep traffic flowing and make sure they're not overloaded - and to make money, of course -, networks charge you for using mobile internet. Instead of paying by the minute as you do with calls, you're billed according to how much data you use.
This makes it important to compare mobile phone deals and choose the plan with a data allowance that best suits your needs.
Do I need a mobile phone plan with unlimited data?
That depends. Plans with unlimited data give you the freedom to do what you want online, but many people don't actually need them.
It boils down to this: do you plan to use the web extensively when out and about? Will you watch films and TV shows on the likes of BBC iPlayer and Netflix when you're not using Wi-Fi? If so, you'd definitely benefit from unlimited data.
If not, you'll probably be fine with a data limit. How much data you need will depend on what you do on your phone. Check out our guide to internet data usage to get a sense of how many gigabytes you're likely to guzzle, and pick a plan accordingly.
What is a fair usage policy?
While mobile phones plans are often labelled as offering 'unlimited' data by networks, the amount of data you can actually use is normally capped by a fair usage policy. This is basically a set of guidelines laid out in the terms and conditions.
Breach the fair usage policy and your mobile phone bill could increase significantly, as additional charges may apply if you've used too much data. The Advertising Standards Authority (ASA) has looked at the networks' use of the term 'unlimited' when it comes to data and given them the green light to keep using it, so be aware of any limits that may apply.
To stay out of the danger zone, make sure you understand your network's fair usage policy. If you think you might breach it, consider ways of cutting down your data consumption - use Wi-Fi where possible, for example.
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