Here is what I discovered today after experiencing the same frustration. When you press the lower right hand key to turn off the phone, a screen opens with 3 options:
1. SILENT MODE 2. AIRPLANE MODE 3. POWER OFF
The screen is sensitive. Be extremely careful as to not touch the middle option (Turn on/off airplane mode) That option is the true indicator of whether your Moment is in airplane mode or not. The "check box" in settings is secondary. Uncheck that as well. Since making this discovery my problem was immediately eliminated.