BT has signed a multi-year mobile virtual network operator (MVNO) contract with EE, formerly replacing Vodafone as an infrastructure partner.
BT will use EE's network to sell enterprise, public sector and SME mobile services.
BT decided to replace Vodafone last Autumn and announced that EE would be its new MVNO partner. The pair have now announced they have signed a multi-year contract for the provision of 2G, 3G, 4G and Wi-Fi capacity.
O2 was also in the running for the contract, before being pipped by EE, which controls the T-Mobile and Orange brands.
The deal will also see EE supply mobile connectivity to BT's employees.
"BT will carefully manage the change from its current UK MVNO provider to EE to ensure a seamless transition for customers," said BT.