The call quality wasn't too good on mine either. I was disappointed. Finally read here that turning OFF Advanced Calling would help the complaints of dropped calls and call quality BUT by doing so, you lose the ability to talk and transfer data (ie browse the internet) at the same time.
I called Verizon. What he did has fixed the problem.
I turned off Advanced Calling (AC).
Turned off my phone.
Verizon rep RESET the AC feature, on my phone, at his end.
Turned my phone back on and turned AC back on.
He gave me his email address and asked me to monitor it for a week.
All calls have been strong and clear! Sounds like I'm on a landline talking to someone across the street

I've made exactly two phone calls with the S7 while in Walmart. The first (before Verizon reset AC) was
so bad I just had to hang up. Today (after Verizon reset AC) it was a strong and clear connection
Here is a link to to another thread on this topic...
http://forums.androidcentral.com/samsung-galaxy-s7/660108-three-dropped-calls-s7-never-dropped-calls-note-2-a.html