T-Mobile was running a promotion on its Web n Walk mobile broadband plan where you could get the service for £15 a month and the offer ended 31st March 2008. The advertising emphasised that the product had a 3GB fair use policy, but that no matter how much you surfed there would be no extra costs.
The advert had complaints raised about it by BT and a member of the public with the Advertising Standards Authority. The complaints centered over the usage limit, and that BT thought people had to pay to upgrade if they went over the limits.
The T-Mobile response was that the 3GB figure, was not a fixed limit, but part of a fair use policy with the service continuing to work but at a slower speed if you exceeded 3GB of download and upload traffic in the month. This reduced speed applied for 14 days, if someone continued to abuse the fair use policy they would have their speed permanently reduced. Once the speed is permanently reduced the only way to get the speed unlocked would be to regrade to a different tariff.
The ASA decided to not uphold any of the complaints. As far as we are aware T-Mobile is the only mobile broadband provider that operates this way, with other providers if you exceed their bundled usage allowance an excess usage fee which can range from £15 per GB to £100 per GB will apply. The adverts make the excess charges look smaller by quoting figures of 10p per MB, relying on many customers not being aware of how fast even just surfing the web can eat through 50 or 60 MegaBytes of data.