iPhone4, running hot, fast batt drain and HUGE data usage. Help!

[baskie]

First off I realise these sorts of questions are not really meant for here, but I trust the replies I get here over places like the Apple forums, so please bear with me.

I have a friends iPhone4. Not JB's. Running 4.3.1, on o2 in the UK.

She reports the batt rarely lasts a day, it regularly gets hot, hangs often and data usage is thru the roof, she knows this as she keeps getting texts from 02 warning her!

Phone is two months old, previously she was on a 3g, uses the new phone in the same way and as much as the old one, and never had these issues on the 3g.

Reset been tried. Restore tried. Looking in settings nothing seems obvious, no apps seem to be hungry for battery power and data, I'm no expert but all seems normal to me.

Before it goes into Apple, any one any ideas for things to check/try?

Ta.

[i.Annie]

Try a restore to 4.3.3. That's probably the best solution. If that doesn't help the problem, it's time for an exchange. Excessive overheating can occur due to hardware failure or manufacturer defect. Better to just get an exchange.