In an email to customers, O2 says its own network of more than 8,000 wi-fi hotspots will still be available in various shops and restaurant chains.
BT Openzone has five million hotspots but O2 says that only 4,200 of them were ever shared with its customers.
It means O2 will lose around one third of its current wi-fi hotspot network.
The change is the result of a four-year agreement between the two telecoms firms coming to an end on 30 June.
“From 1 July 2013, we will no longer offer access to BT Openzone wi-fi hotspots to our customers,” said O2 in a statement.
“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 outdoor and indoor locations across the UK.”
read more at BBC News