Hi NickitaPir,
We understand that you're having an issue with the microphone and hearing the caller on your iPhone since updating to iOS 14. We'd be happy to provide you with some information that can help.
Let's try the steps mentioned in the following support articles that can help with what you've been experiencing with your iPhone.
If the microphones on your iPhone aren't working
If you hear no sound or distorted sound from your iPhone, iPad, or iPod touch speaker
If this is not what you're experiencing, please respond back with additional details.
All the best.