how can I turn off everything of child's phone except for call and text?

Family mode and allowance does not work. Please stop promoting crap features. 

Doesn’t iMessage require data to send and receive messages as well?  

magentatechie wrote:

 

The absolute easiest way to stop the data: Log in to T-Mobile.com, select his line, choose Manage Data and Add-Ons, then change his data feature to “No Data”.  You can change this back at any time if you wish.

 

Hope this helps!

When I try to do this, I get a message that I turn off his cellular data plan, that plan is no longer available and can’t be turned back on. So it sounds like I’d have to switch him to a new plan to do this which sounds complicated.

T-Mobile offers a Talk and Text only plan that does not include data at all, but if you have Wi-Fi in the home, he’ll still be able to use it.  

Family Mode does allow you to control data usage, but again- access to Wi-Fi means he’ll still be able to get online.  There is an additional Family Mode Home Base that you can connect to your router and control his access to the Wi-Fi. 

Alternatively, and I’m sure other ISPs offer a similar service, but the Comcast XFinity app allows you to view all devices connected to your home internet gateway and you can *pause* the data to that device, which is much easier than changing the Wi-Fi password.

The absolute easiest way to stop the data: Log in to T-Mobile.com, select his line, choose Manage Data and Add-Ons, then change his data feature to “No Data”.  You can change this back at any time if you wish.

Hope this helps!

You can try Family Allowances but if he’s that smart he’ll probably figure out a work a round since you can’t shut off the Wifi of the phone.

Easiest way would be to take the phone away and give him a basic phone to use.