You can use two SIM cards with different phone numbers in a Dual SIM phone at the same time. Depending on the model, you can be reached on both SIM cards at the same time, or you can switch between them. This comes in handy if you have both a business and a private number, or a domestic and a foreign number. It depends on your device whether you can set up a separate ringtone for each phone number.
Switching between SIM cards and contacts is very easy, so you're always calling from the right number. The contacts are often sorted by SIM card. This way, you will always call your business contacts with your business number and private contacts with your private number. In a Dual SIM phone, you can also use only one SIM card.
If you are returning or sending an Android device for repair, it is necessary to remove your Google Account from your device. To delete your Google Account, follow the steps below:
Some phones have the front camera and proximity sensor in the display. The proximity sensor flashes as soon as you bring your phone closer to your ear. It then looks as if you have a dead pixel in the display.
That flashing white pixel is not a dead pixel but the proximity sensor that does its job of turning the screen off while calling to prevent unintended touching.
As a rule, water damage to any electronic equipment is not covered by the warranty. This is because water damage falls under user damage. The manufacturer cannot give a guarantee on this, because they cannot influence the use of the appliance.
Many devices, such as smartphones, smartwatches, and fitness trackers, have a watertightness certificate indicated by a code, such as IP68 or 5ATM. Water damage with these certified waterproof devices is also not covered by the warranty. This is because the waterproof seal of your device may be subject to wear and tear due to normal use. So always try to prevent your device from getting wet, even if it is waterproof.
It is possible that TalkBack is turned on and because of this your device does not respond to your touches. This is a feature of Android, made for the blind and visually impaired. In this mode, the phone converts the text on the screen into speech. You can disable this feature from the settings menu, under 'Accessibility'.
Here you can find more information about Google TalkBack.