The source stems from O2 and that's had a knock-on effect as they also supply Sky, Tesco, Giffgaff and it's not just phones that are down - it's everything ran by Telefonica which also affects BT. It's screwed up my work for the day, I can't call or even text anybody or receive messages and despite 02 customer service being free, I can't contact them from my phone because my balanced is rinsed even though it's supposed to cost nowt! So frustrating!