Hi winterlightning28,
If you haven't already, be sure to restart your iPhone. For the iPhone XR this would be done by holding either volume button and the side button, then 'slide to power off'.
You mentioned you'd recieved a message stating 'Not your AirPods?' Was this before or after 'forgetting' them in Settings > Bluetooth? Are there any other AirPods in the environment that your phone could be detecting as well
We would also suggest looking at potential sources of wireless interference which could be obstructing the Bluetooth connection. Try removing any cases from your devices and ensure you are not near any device that could be causing interference. This article will go over things to check for in your environment:
Resolve Wi-Fi and Bluetooth issues caused by wireless interference
Aside from taking these steps, we would suggest contacting Apple Support directly as they will have more specific steps to take and can also offer service options if needed.
Contact Apple Support
Take care.