My daughter has become addicted to her mom's Nokia 3 mobile. She is only 13 and always using facebook and whatsapp, which is not only affecting her studies but has changed her positive attitudes into negative. We have consulted psychiatrists but she told us to keep her away from the phone. we have tried a lot but all are in vain. Please advise us how to deactivate the mobile for some months so that we can go for a small phone without internet facility. Keeping the mobile in flight mode or removing SIM is not a solution for her. We need a solution from settings itself.
You do know that as long as the phone is around and usable, and there is any WiFi anywhere, she can try and use it. I had a kid that was like that for a while. Even turning off the service didn't help because she could use the WiFi. You may want to consider ways to block WiFi on that phone without a password of some sort and place a password on the phone. You can even go into a modems settings and block specific devices from using it. Just so you know.
If your wife plans to keep using it. Or, if you are going flip only, then I would suggest locking the phone somewhere.