I had this issue while using my phone at home as well with a week old iphone 7 plus purchased from the apple store. it was working fine until last night when i could receive and make phone calls but the person on the other end could only hear 'noise' but i could hear them talking fine. the problem persists today.
I contacted apple support and got a person via CHAT (since i could not make a phone call!!) and we did the following,
1. check to make sound works on your phone,
a. using voice memo, record and play back sound
b. ask siri a question, i.e. find 'joe brown' (someone who is in your contact list)
c. record a video, with the front and back lense (i.e reversed and without it reversed)
2. check you connection to your cellular provider
1. turn off your phone, wait 2 mintes turn it back on
2. turn on airplane mode, wait, then turn it back on,
3. enable wifi calling SETTINGS>PHONE (this test did not work for me because I was still connecting to AT & T)
My husband who has a droid could make and receive phone calls fine,
I have lived at my home for 8 years on had an iphone 4 & 5 with the same carrier, AT & T, and never had this type of issue but you'll find apple support wants to say it's a carrier issue.
if you go online you'll find other people have had this issue but you shouldn't have to turn off features, reset your phone or muck with the exterior to get it working, it's not a cheap phone, i would return it
good luck