Make sure your mics are free from any dirt or grim. Give them a clean and try again. Mic quality should be good To excellent.
It is well known by now that mic quality for calls on AirPods Pro is terrible...listening to audio/ANC all good but they have zero ability at isolating external noise. I now carry around trusty EarPods - yes corded EarPods as the call quality is 100% better because the mic is closer to your mouth and you don't have any BT compression issues (c'mon Apple when are you switching to a better BT high definition codec?)
Don't believe me? Anytime I am stuck with only my AirPods Pro needing to make a call I make a quick voice memo to sample how I will sound...If I am in a noisy environment eg. cafe this test usually fails as my voice is a garbled mess of all the noise around me. Switch to EarPods make another voice memo problem solved voice is crystal clear!
Other companies have already solved this issue with a combination of more mics and noise isolation algorithms (but of course many of these headphones are much larger than AirPods Pro). Hopefully this iOS update improves voice isolation as most of us operate in a noisy world AND make phone calls!