As I have previously reported, I have had static over both voices on phone calls with my iPhone 11 Pro, Phonak M90s and P90s, and iOS 13.7 and 14.2. A similar problem has also been reported with Resound and Starkey HAs.
For me the problem is solved, but only for several hours, by rebooting the phone.
OK, a problem with the iPhone, right?
BUT what utterly baffles me is that the problem is also solved by turning off my left HA! (As is the default, my right HA is the one that connects to Bluetooth and the right connects the audio signal to the left.) If I turn off the left HA in the middle of a call, the static disappears. I can’t imagine how this would have any effect on the phone.