AirPod 2 Pro
I have AirPod 2 pro and iPhone XS which have connectivity issues related to phone call. Always disconnecting and making eco to the speaker. Hearing the incoming call in the pro and when answering nothing is heard.
Try the easy steps first, check your iPhone software is fully updated. Settings/General/Software Update.
If you updated the iPhone you should have finished with a reboot. If not rebooted then restart your iPhone. It's a computer and a reboot fixes so many problems. I recommend to go direct to the Forced Reset method.
Restart your iPhone - Apple Support
Try deleting the Bluetooth pairing for your AirPods, and pair again.
Try a complete reset on your AirPods, How to reset your AirPods and AirPods Pro - Apple Support
The method of last resort is Contact Apple Support, but they will want to do all the points above so you might as well be a few steps ahead and save some time if you have to call them.