Humpty Dumpty famously told Alice in Wonderland that "When I use a word it means just what I choose it to mean - neither more nor less." The same can be said of mobile broadband companies that advertise "unlimited" data deals.
In reality, networks see data use rocketing and fear bearing the cost if people really did use as much data as possible on their smartphones. To get round this, they often have a "fair use" policy that limits heavy users. Here's our guide to who does what.
02: This network doesn't advertise unlimited packages; instead users either subscribe to a 1GB or 2GB allowance each month, or buy 1GB on a pay-as-you-go basis. Once the user hits the limit, their mobile broadband cuts off until they buy more data. Customers also get truly unlimited use of BT Openzone WiFi as long as its for personal use and doesn't affect other customers.
Orange: This network also doesn't have unlimited deals: it's biggest package is advertised at 3GB a month. Going above this limit will automatically cost 5.1p per MB. It also offers free BT OpenZone WiFi, though this is also subject to a monthly 3GB limit.
T-Mobile: Unlike most networks the limit depends on how you use data. There is no limit for ordinary web browsing or sending and receiving e-mails. However, there's a total 500MB limit for uploading files, downloading files (as opposed to visiting a web page), or streaming video. If you hit this limit, you can be cut off for uploading or streaming until the next billing period begins. There are no excess fees if this happens. However, web browsing speed can be heavily reduced, in some cases to dial-up speeds. The block on file downloading may also mean large e-mail attachments aren't accessible.
Virgin: The unlimited data deals in fact have a monthly limit of 3GB. If you go over this limit, the company may ask you to reduce your usage. It retains the right to charge you for excess use in the same way as customers who go over limits on cheaper package: the fee for this is £15 per gigabyte (1.46p per MB).
Vodafone: For packages without a publicised limit there is a fair use limit of 5GB a month. If you exceed this limit, Vodafone will ask you to "moderate your behaviour" at first, but retains the right to cut your connection speed, block data altogether or even end a contract.
Note that with all networks, these rules apply to new customers. Depending on when your became a customer, you may be covered by higher limits on your original deal as there may be breach of contract issues if the network tries to change this, especially during a mandatory service period when you've bought a new phone.
