I went out to Hang Hau for breakfast today, with my iPhone in my pocket. When I got back home, my mom asked me why I didn't answer her phone calls.
Hmm... maybe it's because I didn't take my headphones with me this morning? The ringtone is quite hard to hear in all the traffic noise you know. But as soon as my mom did a test call to my phone, I knew the problem is with the phone.
The phone never rang.
The phone was turned on and I could run apps and go online via wifi perfectly in it. There're 2 bars of signal from 3's service. But the phone part of it was like.. disabled! I couldn't call it from landline or from other mobile phones, and it couldn't call out. Worse, while the iPhone was on but not accepting any calls, the caller wasn't able to leave voice messages either. For a moment I was suspecting it was 3's problem. But the phone worked correctly after I rebooted it. So there must be some problem with my iPhone that prevented it from receiving calls and calling out.
The mobile phone part of the iPhone can crash silently. That's a big problem. I don't care too much if SFNetNews or Bloomberg crashes - though I would really appreciate it if Apple can stop them from crashing; But why can I miss calls with my phone turned on, connected with cell towers?
I tried to replicate the problem by killing the MobilePhone app in my iPhone and calling in, after the reboot. I could still hear the ringtone and answer the call, however. Something much more complicated than just an app crash must have happened this morning. Not enough memory left for the incoming call?