Orange and T-Mobile have announced that customers on both networks can now roam with either operator, without incurring the charges often associated with traditional network roaming.
The companies said on 6 September that the opt-in service would go live on 5 October.
Orange announced on its website on Tuesday: "Now Orange customers can use T-Mobile signal too...You'll know when you're using T-Mobile signal because you'll see 'T-Mobile' on your screen - other than that nothing else changes."
T-Mobile customers saw a similar message on the official website: "Now you can sign up to pick up a signal from Orange when you don't have a T-Mobile signal, so you can call and text in even more places."
Both providers say that call charges will remain the same regardless of which network a user connects to. Orange notes that some handsets might display a roaming symbol when using the T-Mobile network, but that this can be ignored and that "you definitely won't pay any extra to use your phone in the UK."
The arrangement currently covers only text, voice and 2G data but the companies plan to support dongles and 3G data "in 2011".
Orange customers will still be able to call their nominated 'Magic Numbers' for free when using the T-Mobile network but will only be able specify other Orange customers as new Magic Numbers. Similarly, T-Mobile customers will not get access to the Orange Wednesdays promotion that gives Orange customers 2-for-1 cinema tickets on Wednesdays.
To register for the network sharing feature, both Orange and T-Mobile customers need to enter their mobile number and handset info on the respective websites. Both operators recommend enabling 'automatic network selection' to most easily make use of the roaming option.
The cross-network roaming currently only covers the UK, meaning that connecting to anything other than your normal parent network outside of the UK will incur standard roaming charges.
In May, the two networks announced that the back-office amalgamation of the companies would be named Everything Everywhere but that each would retain their own separately branded operations.
"[Everything Everywhere will be] a single super-network that will give bigger and better coverage for customers, with a smaller impact on the environment", it said in its announcement at the time.