Follow these steps to change which number on your dual SIM iPhone is primary and secondary.
- Go to Settings > Cellular.
- Set your default number.
- On this screen, choose a number to be your default, or you can choose which number is to be used only for cellular data. Your other number will be your default.
- Use Primary as your default line: If you select this option, Primary will be used by default for voice, SMS, Data, iMessage, and FaceTime. Secondary will be available just for voice and SMS.
- Use Secondary as your default line: If you select this option, Secondary will be used for voice, SMS, Data, iMessage, and FaceTime. Primary will be available just for voice and SMS.
- Use Secondary for cellular data only: You might want to select this option if you're travelling internationally and you want to keep Primary for voice, SMS, iMessage, and FaceTime. This will allow you to use Secondary for data.
