iPhone 4s net woes

Spent half the day trying to fix a broken network on a brand new iPhone 4s.
For those in a hurry the ONLY way I could find to fix it is the magic "reset-all trick":
Settings>General>Reset>Reset all Settings
And now for the details.
Woke up this morning connected to my home wifi, no probs. As soon as I left the house I couldn't connect despite a full (KDDI) antenna signal and a 3G icon. Phone was fine, just mail, and all web access couldn't connect.
Strange I thought, waited until I got to Shinjuku hoping it was a local prob. Still no go so I called KDDI info where they took me through these steps:
1. Stop and start network via airplane mode.
still no go...
2. Reset network Settings>General>Reset>Reset Network
still no go...
3. Reboot iPhone
still no go...
4. Then I was told to reset the phone to factory & restore from an old backup!!!
so I went back to the office ready to do that meanwhile losing a week of setting up this baby. Awful.
Did that and got connected!
Until I left the office, when my office wifi was out of range I was off the net again.
Went to various meetings by calling friends and asking them to get addresses where I had on my net based contacts!
Finally I went to a KDDI shop, they went thought exactly the same as above, finally telling me I had no choice but to go to Apple. Typical pass the blame game.
Then on the way back I just tried the reset-all trick above and it worked.
The actual prob I have not pinpointed but for now if you are suddenly left without a net try it it may save you a lot of trouble.
Now maybe I should bill those bastards at Cupertino....