iphone 6plus voice problem

Carrier: AT&T

Model: iphone 6s Plus

Purchased: Nov2016

Problem 1: Sometime suddenly my iphone behave very weirdly. Specifically when I receive an call after picking up the call other person can’t hear my voice.

After restarting my mobile issue will get wipe out. In a day it happens number of times.

Problem 2: In a day sometimes when I try to call someone usig my apple headphones.

I can’t hear outgoing ring sound and even if call get connected opposite person can’t hear my voice. If I restart issue will get resolved.

Could anyone please provide me permanent solution.If I’m missing any settings. Else is this hardware or software issue.

FYI...I'm maintaining my iphone very well. not sure why I'm facing such issue.

Thanks

RS