The office is equipped with a Edgewater EdgeMarc 4500 router (Software Version 11.6.18 -- Mon Mar 25 14:01:38 PDT 2013). I did a test and determined that the router is slowing down the internet from 17 Mbps to 3 Mbps:
...and as I was writing this question, I did some more digging and found this:
Turning off traffic shaping fixed the problem. Should I leave it on but change the vaules? What should the values be?
This is a small office with 3 VOIP phones and a max of 3 people, usually 1, working.