I have an apple aphone 7 plus, people cant hear me when I try talk on the phone

If you have a case on the phone, try without it. The case may be covering the noise cancellation mic on the back of the phone near the camera. Also try with a headset. Does the problem exist with it? How about using the speakerphone? If none of these resolve the problem make a genius bar appointment: Genius Bar Reservation and Apple Support Options - Apple

You can't make an appointment online or even chat with anyone.. Apple disabeled all that