(Telecompaper) UK mobile operator EE has announced the launch of WiFi Calling, making calls and texts available in every Wi-Fi connected home and small office in the UK. EE said its seamless service will allow users to switch between calling over mobile and Wi-Fi networks. Designed for home or office use, it does not enable switching between the two in mid-call. CEO Olaf Swantee told the BBC said he expects around 5 million people to be able to use the service by the summer. It will initially is offered to postpaid customers using the Lumia 640 or Samsung S6 and S5 smartphones. The BBC understands that the iPhone 5S and more recent Apple phones will also be supported. EE said it will launch an own-brand budget smartphone integrating the Wi-Fi/mobile switching technology. Customers join the service by sending a text message. Even if a personal Wi-Fi network is used, the customer will be billed as if they had made the call in a normal manner. The service cannot use it to make cheaper calls from abroad.