FiniteAffinity.
Many thanks for a long and helpful response. I'm on O2; as I understand it, O2 don't lock handsets in the way some providers do.
I'm glad you got your problem solved and I'd be a fool not to at least try this line of thought to see if it helps my situation. Hopefully bright raven is seeing this too; it could be good news for both of us.
As it goes I'm travelling soon and will have to get a local sim, so that will give me an opportunity to see if your situation and mine are similar, if you pardon the pun.
Apple's bug reporters informed me, after monitoring my phone's logs of battery and baseband, that with the TMobile SIM, the baseband was crashing every few mins, and restarting - this is what causes the battery drain and "phantom" usage.
I'm interested to know how you got that help; was it in-store or via their phone helpline? I'd like them to run that test for me...
If you can try another provider's SIM, and see if the problem goes away, this will verify your problem. If it is indeed a SIM problem you have, then the only solution at the moment seems to be to get your phone replaced (an apple store genius should do it, regardless of where you bought your phone).
I'm a little confused by this bit. You saw that the sim from your provider was the issue and that other providers' sims were ok, but Apple's response was to change the phone? Is that inferring that they know the readers are not robust and certain networks will have trouble with them? I'm baffled why Apple wouldn't just pass the buck on this one. Very strange. Again, I'm glad for your sake that they did, it seems to have worked in your favour.
One more thing - the serial number of the defective phone began with DNQG..., whilst the new working one begins C39G...
Mine starts DNPG.
Hope you get your problem sorted... I had mine for over a month, and I know how depressing it is having a practically unusable phone.
Thanks for your help.
It seems everyone is experiencing slightly different problems, some are close to others' experiences and others seem totally out-there compared to their own findings. Take this mini back-and-forth regarding sim cards that has cropped up recently. All those non-sim users across the pond will be reading this thinking we're nuts and that sim cards can't possibly be the problem. Who knows.
Excessive usage while idle seems to be the cause of battery drain but that in itself doesn't begin to establish the actual problem or problems.
I'm increasingly thinking that we are not linked in this thread by a common problem but merely a common symptom.