Whenever I leave my home Wi-Fi hotspot, my phone seems to pop up with a notification, asking me if I want to go in to roaming mode (or something along those lines - I can't remember the exact phrase and I can't recreate the notification without leaving the house). I've only noticed this when I've come to pull the phone out of my pocket. I tell it to just carry on using my mobile network for data connectivity. When I return home, instead of returning to the Wi-Fi network, it carries on using my mobile network for data connectivity. How do I get the phone to automatically switch to using my mobile network for data when I'm not in my hotspot and then to automatically switch back to it when I am in the hotspot? It's driving me mental at the moment, and there doesn't appear to be anything obvious in the phone or any documentation! What do I need to do for network connections to be implemented automatically?