Learn how to use the Mobile Device Unlock code of the Microsoft Lumia 640.
SIM unlock phone
- Determine if your device is eligible to be unlocked: Unlock your wireless mobile device.
- Contact Customer Care to request the Mobile Device Unlock code for your phone.
- Turn on the phone with the non-T-Mobile SIM card. The device displays "Please input unlock code."
- Enter the unlock code. If successful, the device displays "Phone is unlocked."
- Stop if you receive an error message. The device may lock permanently if the incorrect code is entered multiple times.