This also depends on what model they have.
Identify your iPhone model - Apple Support
If the model is only able to be used on GSM networks it won't be able to be used for all networks. For example, an iPhone 7 model A1778 could be unlocked, but would only be able to be used on AT&T or T-Mobile. It's physically impossible for this model of phone to be used on a CDMA network.
This also depends on what model they have.
Identify your iPhone model - Apple Support
If the model is only able to be used on GSM networks it won't be able to be used for all networks. For example, an iPhone 7 model A1778 could be unlocked, but would only be able to be used on AT&T or T-Mobile. It's physically impossible for this model of phone to be used on a CDMA network.
Connect it to your computer and restore it as a NEW device (not from your backup) in iTunes. You will get a message "Congratulations, you iPhone has been unlocked".
You can check with Apple Support which can let you know what activation policy is on the phone and whether it compatible with sim you are trying to use.
I recently factory unlocked my 6s and looks like I must unlock through ITunes as well. When I put another providers sim, it does not read the network. What can be done?
