What is the WAN IP address range that you are typically assigned? Reboot your modem a few times and check each time to see a few different IP addresses. I suspect they are limiting users of this plan to slower parts of their network. I only get IPs in the range 59.94.[148,149,150].x while my neighbours on other plans, and even my connection before switching to this plan, would be assigned IPs from other ranges too like 61.x.x.x and the newer 117.x.x.x.