How to improve call sound quality on AirPods Pro 2?

My AirPods Pro 2 are my favourite Apple device. Sound quality is excellent when listening to podcasts, music etc. But when I make or receive a phone call, the sound goes quiet intermittently to the extent the caller thinks my phone signal is poor. Disconnecting the aipods and resuming the phone call is faultless. So it can’t be Bluetooth as the podcast test proves. I’ve reset the AirPods back to factory settings, I have the latest AirPod firmware and iPhone 16 Pro ios18.5 and I’ve ensured no other phone is in my possession. If it is, I disconnect that phones Bluetooth anyway. I’m stuck. I’ll probably be advised to take to a Genius Bar but unsure what can be done that I haven’t already tried.

any thoughts please?

[Re-Titled by Moderator]

Original Title: Airpods Pro 2 - loss of sound quality on call