How do I improve MagicJack call quality?

[laredotornado]

I'm using MagicJack on a MacBook Pro (OS 10.12.3, Sierra). Frequently when I use magicJack, people will complain that they cannot hear me well, although I can hear folks fine. I am connected to the Internet wirelessly, although my speeds (measured through speedtest.net) appear fine ...

download - 16.493 Mbps
upload - 4.15 Mbps

Also I notice when I make phone calls on Skype, there are no problems either hearing the person or being heard. What other things can I try to improve the quality of my magicJack calls? I'm located in Chicag, Illinois if that is worth anything.

- Dave