From July, O2 broadband and mobile customers will not be able to access free Wi-Fi at BT wireless hotspots.
O2 customers will soon lose access to free Wi-Fi provided through BT.
Many of O2's customers get free wireless broadband at BT Wi-Fi hotspots, but, from July, they will only be able to access the 8,000 hotspots owned by O2.
BT Wi-Fi, formerly known as BT Openzone, has five million hotspots in locations across the UK, however, only around 4,000 of them were ever accessible to O2 customers.
To help customers understand the change, O2 has published an FAQ.
A spokesperson for O2 told broadbandchoices.co.uk: "From July, we will no longer offer access to BT Wi-Fi hotspots to our customers. We now have over six million users on O2 Wi-Fi, who can access over 8,000 hotspots across the UK.
"We'll continue to extend the reach and scale of O2 Wi-Fi through exciting partnerships with venues including O2 shops, restaurants, retail outlets and both outdoor and indoor locations."
O2 customers who currently have access will still be able to use BT Wi-Fi free of charge until Monday 1 July, 2013. Those who wish to continue using the hotspots will need to re-register and pay for their wireless access directly through BT.
BT revealed recently that during the past year 13,000,000,000MB (13 petabytes) of data was consumed by people connecting to BT Wi-Fi hotspots across the UK.