When your iPhone is fully turned off does it still use data?

I have used almost all my data and I have 9 days to have no data unless it is very important, but for next time when I'm at school if I turn it all the way off will it not use data or do I have to do in settings and turn it off there
Cuz I rather just turn my phone alway off and it not use data
Does it work that way

When it's 100% off it should use 0 data
But you can also keep it in airplane mode that will also use no data

No. If it is off, then it can't send or receive anything until it is turned back on.

Of course not, this is one of the dumbest questions I've seen on here.

Well it wouldn't have any power to use anything let alone data. You could just go into Settings & turn off the Cellular Data so you wouldn't have to make the phone a brick just to avoid data charges.

Using Airplane Mode would also achieve this, but it also turns off the carrier network, so you wouldn't be able to get calls, texts either.