BT Openzone's Wi-Fi roaming deal with The Cloud will end on Thursday, after the two communications firms failed to resolve unspecified issues over commercial terms.
BT and The Cloud have had the deal for five years, but customers of each network will no longer have access to the other network's hotspots from 9am on 2 October.
The deal's expiry could drastically cut the number of hotspots BT Openzone customers can use, particularly in business-centric areas — The Cloud has 6,500 live Wi-Fi hotspots in retail venues, hotels, airports and sports and music venues, while BT has only 3,000 Openzone hotspots.
BT is claiming that this shortfall will be mitigated by the roughly 140,000 users who opened up their routers into effective hotspots following BT's deal with the Wi-Fi-sharing community Fon. These are, however, mostly residential users. BT has introduced a similar concept for its 170,000 business customers, but there are as yet no figures for how many have volunteered to open up their routers to the public.
BT's Wireless Cities programme, which covers 12 UK city centres, could also make up for some of the coverage lost through the deal's breakdown. There will also be many sites where BT Openzone and The Cloud coverage is currently duplicated.
"It's disappointing for BT Openzone customers that they will no longer be able to benefit from the convenience of our hotspots," a statement sent to ZDNet.co.uk on Monday by The Cloud read. "We are disappointed that BT could not reach acceptable commercial terms."
The Cloud is now trying to tempt BT Openzone customers to switch by offering them 30 days' free subscription if they sign up to The Cloud.
Other operators that continue to have roaming agreements with The Cloud include O2, Orange, AT&T and iPass.
Steve Nicholson, The Cloud's chief executive, also pointed out in his company's statement that The Cloud remained "reliant on BT for PSTN among other services and will continue to work closely in the hope they reconsider their decision for the better of their customers".