you need to isolate wetyher or not its a hardware issue.
make a voice memo. (if there is sound then, your bottom mic is fine.)
Make a video (if there is sound then your speaker mic is fine.)
if those dont work restore to factory settings and setu p as new, if the issue persists, setup replacement
if you have sound, try resetting your network settings. (settings general>reset>reset network setting THIS WILL DELETE ANY SAVED WIFI PASSWORDS.)