Is Cellular Network Data Usage persisted to a new iPhone
I got my original 3GS on release day in June 2009 as an upgrade to a 1G. In around September 2009 it developed a problem with the mute switch so I had it replaced at my local Apple Store.
A friend just asked me what my data usage is (as he is looking at his first smart phone contract and doesn't know how much data allowance to include) so I checked my stats on the 3GS.
It says at the bottom Last Reset: Never so my question is, when does Never begin?
My current 3GS was restored from the backup of my original 3GS when it was replaced and I'm not 100% sure but I think that the original 3GS may have been restored from the 1G.
Does my usage stat include only the current 3GS or does it include the original 3GS usage (and possibly the 1G usage if I restored from it) as well?
EDIT: Following Cawas's answer, here are my current stats for illustration:
Apple apparently has no official information about this and, given your stats, I now believe we simply can't know about it without an app.
If all you want is get to know your data usage the safest way is checking it with your carrier, because the iPhone data really isn't all that precise. Another option would be jailbreaking your phone and using some cydia app such as Data Counter, Download meter or even SBSettings, which would still use the iPhone data and still wouldn't be as precise as your carrier can be.
Now, if you're fast enough you can even get some app for free, on the Apple Store, though DataMan Lite might be enough for your needs.
Since iOS 1.1 the data history is stored as part of the iOS backup in iTunes, so when you get a new / wiped iPhone, this data gets replaced with the data from your last backup if you restore a backup to the iPhone.
Details are in the history section of iPhone and iPod touch: About backups
Knowing this it is quite possible you could use some data between the time you started a new device by putting your SIM card in it and lost that from the total when you restore from a backup that has old data. (Just like a restore will wipe the contacts you add on a new phone and then go to restore it with the contacts as they were from an earlier backup.)