Making phone calls from Apple Watch

When I make an outgoing phone call from my watch, the microphone does not seem to work. People on the other end cannot hear me at all. When they call me and I answer on my watch, they can hear me clearly.

I've tried restarting both my phone and my watch but this has not helped.

I've also tried unpairing and repairing my phone and my watch. This has not helped.

Both devices are up to date.

Any one got any ideas please?