The campaign is a joint collaboration between Fallon and Saatchi & Saatchi and details how the 27 million customers across both Orange and T-Mobile can now access both networks to make calls and send texts from UK locations at no extra cost.
Ads will appear online, outdoor on billboards, bus headliners, taxis and the London Underground, as well as in the press for the next three weeks.
The campaign features two separately branded ads having a conversation with each other. For example, the Orange ad announces that "T-Mobile customers can now use our signal", while its twinned T-Mobile ad replies "Ditto".
Other headlines include "Orange customers can now use T-Mobile's signal too. Signalfest!" and "Who said pink and orange don't go together?".
The copy "Inspired by Everything Everywhere" is included within each ad to represent that this customer benefit was delivered through the creation of the new company and to help customers understand why they will now benefit from access to both brands' networks.
Spencer McHugh, brand director for Everything Everywhere, said the new campaign shows "the unique and unrivalled opportunity Everything Everywhere has to deliver bigger and better ground-breaking customer benefits and campaigns".