I want to reset my Lumia 640 to 8.1 in order to get wifi calling. But I have two questions about that:
- Will Windows Update automatically update to Windows 10 whenever I update the phone, or will it just update to the latest 8.1 build?
- My phone was bought as an AT&T phone and they then gave me the unlock code. Will I need to unlock it again? If so - Will the original unlock code that they gave me work again, or is it a one-time code and I'll have to hope they'll give me a new code again?