Depends on the cell provider. Be sure to shut down all access to cell data or it could cost you a fortune.
Do realize if you do shut down cell data then several functions, including Siri, etc. will not work unless you are connected to WiFi. Turn by turn directions in the new maps app won't work at all.
Using an iPhone without a wireless service plan
If you upgrade your iPhone to a newer model, you can continue using your old iPhone without an active cellular service.
Follow these steps to use your iPhone without a wireless service plan:
- Insert the SIM card from your new, activated iPhone or one that was previously used to activate the original iPhone.
- Connect the iPhone to iTunes on a computer connected to the Internet.
Once iTunes activates the device, you're free to use the iPhone as if it were an iPod touch.
Note: It may be necessary to repeat this process after updating or restoring the device.
iPods use wifi all of the time without cellular connection.