This is the latest example of consolidation in the UK mobile market.
In 2010, Orange and T-Mobile emerged to create EE, which itself was taken over by BT in 2016.
Then, in 2021, the CMA approved a £31bn merger of Virgin Media and O2.
Those deals were followed by job cuts. EE axed 1,200 roles in the months following the merger of Orange and T-Mobile, then an additional 550 jobs the following year.
Vodafone and Three have previously claimed their merger will create thousands of new jobs.
But the union Unite has warned in the past that the deal could add an extra £300 a year to customers' bills, and lead to "up to 1,600 jobs" being lost.