Over the years we have seen a steady trickle of enquires about excess usage billing with the BT Broadband services, where people are convinced their connection usage has not changed significantly but usage has rocketed. Thus it is good to see BT putting their hand up to a billing mistake that has meant for some people excess usage charges were raised when BT-WiFi and/or FON usage took them over their inclusive usage allowance. In theory the BT WiFi and FON usage should be not be counted towards a users monthly total and while the number who got billed extra may be small, it is possible others have escaped being billed but have seen spikes in their monthly usage figures.
The way we all use our broadband connections is changing, and as simply a thing as upgrading from a feature phone to a smart phone with all the weekly app updates that occur can easily boost broadband usage without people realising the volume of data used. The general advice is to buy an unlimited service or if using a service with a usage limit ensure the provider has robust systems in place to notify you of your progress to the monthly limit and any excess usage.
Mobile phone providers in theory have notification systems in place for when you go roaming, but even with all the pressure from the EU it still appears that the text message alerts on the costs when roaming are slow to arrive or never make it.