There's not enough masts to cope. Everybody keeps screaming out "I don't want a mast in my road"etc but then cry when they can't get a signal. Well, there is limited capacity the masts can deal with. I use TuGo at home, technically it's supposed to use your WiFi and not masts, many times I'll get a voicemail pop up and missed call even though the phone is with me all the time and has never actually rang-nothing is perfect in these days of modern technology.