Limit the phone numbers that you can call
When you set up and use fixed dialing numbers, you can make calls and send text messages (SMS or MMS) only to the
phone numbers that you add to the fixed dialing numbers list. For example, if you give your device to your child to use, you
can limit the phone numbers that your child can call. To use fixed dialing numbers, your service provider must set up your
SIM card for this feature. Depending on your service provider, this feature might not be supported.
In the Phone app, in the upper-right corner of the screen, tap .
Tap Settings > Calls > Fixed Dialing Numbers.
Tap Enable FDN.
Enter the SIM security code provided to you by your service provider.
Tap FDN list > > Add contact.
Type a name and phone number.