Traffic shaping for VoIP

Hey all,

Please forgive the naivete of a reddit newbie but I thought this might be the best place to ask a quick question. My company has several offices interconnected via MPLS from CenturyLink. Internet connectivity for all offices is a single firewall that CenturyLink manages & houses.

We've begun to roll out some Polycom IP phones with hosted service. It seems to be working well in larger locations with more bandwidth however none of my locations have a terribly large amount of bandwidth given the costs involved. (10-50 Mb depending on office size.) I've approached CenturyLink about configuring QoS to ensure priority for the VoIP traffic however what I get back from them is discouragement stating that it would be a fairly massive undertaking. It feels like they're not interested in going down this path which is a bit maddening. I'm wondering if there is a solution that I could implement in each office between the LAN and the ISP's router to do some simple traffic shaping to ensure that someone downloading a large file doesn't kill voice traffic. Would something like a pfsense be a good fit here? I'm interested in your take on this.

Thanks!

-DX