Probably you ran out of BT Openzone miniutes, according to the
http://www.btfon.com faqs:
How does BT Openzone relate to BT FON?
BT Openzone provides public wi-fi broadband access at prime locations such as airports, restaurants and city centres. BT FON is an initiative between BT and FON that allows customers to share their broadband connection with each other and BT Total Broadband customers who are members of BT FON can access BT Openzone hotspots as well as BT FON home hubs with their BT FON allocated wi-fi minutes...
I already get 250 minutes per month BT Openzone access through BT Total Broadband, how will this change?
By joining BT FON you will get at least 250 minutes of access (Options 2 and 3 receive more) that can be used at BT Openzone sites and in thousands of new places around the world. When you have run out of these minutes, you can buy additional access.
I have run out of minutes, what can I do?
You can either upgrade to a higher BT Total Broadband Option and you will get your new allowance of minutes from the moment you upgrade. Option 2 gives you 350 minutes and Option 3 gives you unlimited* access. Alternatively, you can purchase additional minutes at
http://www.btopenzone.com/buy or via the buy link on the landing page at a BT FON hotspot.
*(Option 3 customers get unlimited access in BT FON hotspots and 500 minutes per month in BT Openzone hotspots)
BUYING MORE BT FON ACCESS
If I run out of my monthly BT FON minutes, can I buy more minutes?
If you used all your BT FON minutes for the month, you can buy more minutes through the landing page at a BT FON hotspot. You can either buy Wi-Fi minutes by sending an SMS text message or buying them online with a credit card. These will be FON minutes which can be used at BT Fon hotspots. You can also buy BT Openzone minutes online through the landing page. These will also give you access to the BT FON network.
How much does it cost me to buy extra BT FON minutes?
Purchase BT FON minutes through SMS text messaging will cost £1.50 and this provides you with one hour of Internet access. You can purchase FON vouchers online with your credit card for £3 which will provide you with access for 24 hours. BT Openzone has a range of vouchers that you can buy based on your usage needs.