iPhone 7 Plus speaker icon greyed out after iOS 15.7 update

Hello everyone.

i just updated my phone to ios15.7 and realized there is issue with the phone app.

the speaker icon is greyed out. I cannot make any calls or receive any calls. During call, the line is connected but I cannot hear anything nor the receiving party can hear.

voice notes, Siri and any app that utilizes microphone has issue.

can anyone advise on this. I am very sure it is 15.7 causing this. It is frustrating not able to use the basic function of a phone!