1. From your desktop or tablet, go to att.com/deviceunlock.
2. Read and agree to the eligibility requirements to unlock your device.
3. Complete and submit the form.
4. You’ll receive a confirmation email with your unlock request number.
5. Select the link in the email within 24 hours of receipt to confirm your unlock request.
6. AT&T will respond within two business days.
7. If your request is approved, AT&T will email an approval email. AT&T may reject your request or require you to send in additional information.
8. After you receive the email approving your unlock request, remove the AT&T SIM card and insert the new carrier SIM to begin set up.
Once your iPhone 6s is unlocked, you can use your iPhone on another carrier by following the instructions below:
1. Power off your iPhone.
2. Remove the existing SIM card from your phone.
3. Insert the new SIM card (from the different carrier) in the SIM card slot.
4. Restart the iPhone.
5. After the iPhone restarts, follow the on-screen instructions to complete the setup process.