I have LG G3 D850 and I'm still on android kitkat 4.4.2
I want to update to Marshmallow but it always says "your device is up to date"
Please let me know if there is any solution
We can definitely provide you with the steps to update your device's software. You can Learn how to update the software for your LG G3 here. Let us know if this helps.
Sean, AT&T Community Specialist