From what I can tell there is no way to improve the quality accross the ISP's network. Luckily the calls stay within one node on their network so I think that I have the best situation possible as the ISP goes.

After this problem appeared from someone downloading a large movie file on our LAN and maxing out the ISP bandwidth I would like to improve the QOS of the LAN so this can't happen. I don't want to spend a bunch of money though since I think a fiber line between the two locations is in the future. Although even with this fiber line there will still need to be QOS on the LAN.