Many Apple users have already updated their i Phone/i Pad to the latest version.
Originally released in June of 2007 and discontinued in 2008, the first i Phone was made obsolete by Apple back in 2013, and it has not received software updates since the 2009 release of i Phone OS 3, later renamed i OS 3.
According to ATT, shutting down its 2G network frees up valuable spectrum for future network technologies, including 5G.
Alternatively you can toggle “Airplane Mode” from control center. Please note the backup you just took on i OS 9 won't be compatible with i OS 8.4.1, it is just for security purpose.
Take a complete backup before downgrading to i OS 8.4.1 as you will lose all your personal data.
6) Your Apple i Phone 6 restarts.7) Test your device to see if the issue is resolved. Note: You will need to reconnect to your local Wireless network after the reset.