How to hard reset iPhone XR

1. There will be a volume up button on the left side of the phone. You have to press once
2. After that you have to press the volume down button once.
Please remember that you should not press both of them at a time. But you should press them quickly without much delay in between.
3. Then you have to press and hold the button on the other side which is called the power button till the Apple logo is visible on the screen.
If you are not able to hard reset the phone by the above procedure you should talk to the customer care services of Apple and take their advice.

Press on the Volume Up button located on the left side of the phone and let go.
Press on the Volume Down button and let go.
Press and hold the side button until the Apple logo appears on the screen.
You need to press the volume up button and volume down button very quickly, but not at the same time.

The method of using volume up and down buttons along with the power button are applicable for many iPhone models including iPhoneXR. Generally, the method works as it is simply operating the volume button by quickly pressing 'up' position first followed by 'down' position and then pressing the power button till the logo comes on the screen.
In this method, the data in your phone will not be lost and all the files would be available as they were there. The phone would reset and start.
Sometimes if the volume switch has some contact resistance then it might not work properly and such a situation would arise. It generally happens due to a humid atmosphere and dusty environment. If you keep the phone in a warm and dust-free environment then the doubted humidity might evaporate and the switch would work. Alternatively using this method a few times also can give a result in one of those attempts.
If nothing works and you can sacrifice the data or copy it beforehand then a factory reset can also be attempted.
For doing a factory reset you have to go to Settings, Select General, Tap on Reset, Select 'Erase All Content and Settings', Enter Your Passcode, and Confirm to Proceed.
The last resort is of course to go to a service centre or authorised repair agency.