Bought an iPhone 5 the other week and it's been fine so far. Tonight, I tried to make a phone to my other half. It was absolutely silent and yet could see the time ticking away. I tried again, and again, and again. Then eventually she rang me and it worked. Then went silent. Tried a few tests calls that have failed, went through and failed. Just speaking with my father and it went absolutely silent at my end, he rang me back and said he could hear me saying "Hello, hello?". Trying to diagnose if this is a network issue (doesn't seem to be low signal) or something with the phone? Any help or ways to diagnose what's happening is welcome Cheers.