Removing the SIM or putting in an inactive SIM will allow you to use the iPhone as a free WiFi-enabled sixth generation iPod.
Removed SIM and replaced it with an invalid, unactivated, no-account SIM: Still works as 6G WiFi iPod. Still Synced properly to iTunes. Tried placing call. It failed (as expected).
Removed SIM entirely: It complains but works at 6G WiFi iPod. Tried placing call. "No SIM card installed". Failed. Connected to iTunes. Synced without any problems I could detect. WiFi fine.
Removed activated SIM and placed into a cheap disposable AT&T cell phone: Worked fine. Was able to place calls. Good way to save your iPhone from danger on ski or bike trips.
Placed SIM from cheap disposable AT&T Pay as You Go phone into iPhone. Call failed. WiFi fine.
Removed SIM and replaced it with an invalid, unactivated, no-account SIM: Still works as 6G WiFi iPod. Still Synced properly to iTunes. Tried placing call. It failed (as expected).
Removed SIM entirely: It complains but works at 6G WiFi iPod. Tried placing call. "No SIM card installed". Failed. Connected to iTunes. Synced without any problems I could detect. WiFi fine.
Removed activated SIM and placed into a cheap disposable AT&T cell phone: Worked fine. Was able to place calls. Good way to save your iPhone from danger on ski or bike trips.
Placed SIM from cheap disposable AT&T Pay as You Go phone into iPhone. Call failed. WiFi fine.