So I did more digging and learned that is also the phone number of a group called American Muslims Vote
He’s had the (202) 279-0806 number since at least 2013, prior to that (2011) only New York numbers.
https://web.archive.org/web/20130924200424/http://kmkhanlaw.com/Contact_Information.html
I checked the D.C. address given and it was sold May 7, 2013. It’s a residential condo address. The current kmkhanlaw.com contact page does not list a D.C. number.
https://www.taxpayerservicecenter.com/RP_Detail.jsp?ssl=0540%20%20%20%202621