Mobile operators Orange UK and T-Mobile UK have announced the completion of their merger, with the two operators now acting as one under the name Everything Everywhere Limited.
Tom Alexander, chief executive of Everything Everywhere Limited, said: "The formal integration of our new company, Everything Everywhere Limited, is another major milestone and reflects the rapid progress we have made over the past nine months.
"Today we have created the country's biggest communications company, and as the new leader in the industry, it is our aspiration to give our customers instant access to the world around them, to everything everywhere, through both of our brands, Orange and T-Mobile," he added
The pair first announced plans to merge in September last year and were finally given the go-ahead by the European Competition Commission in March.
However, the Commission agreed to the deal on condition that the two companies change their existing network sharing agreements with a third smaller player, Hutchison Whampoa's 3, to "ensure that there remain sufficient competitors in the market".
With a total of 16,500 staff, Everything Everywhere claims to be the largest telecom services provider in the UK.