my headphones are accessory not supported

Try force restarting your iPhone XR. Press and very quickly release the volume up button, press and very quickly release the volume down button, then press and hold the side button for about twenty seconds. When the Apple logo appears, release the button. The timing is a little tricky, so try it a few times.

Some other things to try - If you see an ‘Accessory may not be supported’ alert - Apple Support

Sorry to hear that. You can contact Apple Support with the options below if you want-

• Call Apple at 1-800-MY-APPLE or Apple Support at 1-800-APLCARE
• Chat using the Messages app on your iPhone or Mac. Make sure to use Safari to open the link.
• Contact - Official Apple Support
• Find Locations - Apple