Microsoft Lumia 640 LTE Single Sim - Manual (Page 11)

Help and tips
There's a user guide in your phone – it's always with
you, available when needed. Check out videos, find
answers to your questions, and get helpful tips. On
the start screen, swipe left, and tap Lumia Help
+Tips. If you’re new to Lumia, check out the section
for new users. Make sure to keep the Lumia Help
+Tips app up to date.
For the online user guide, even more info, a user
guide in another language, and troubleshooting
help, go to www.microsoft.com/mobile/support/.
If your phone doesn’t respond
To restart the phone without losing your data and
settings, press and hold the power key for about 10
seconds. The phone vibrates and restarts.
You can also remove and replace the battery, and
switch the phone on.