First thing I would check are the speeds direct to the modem. The fact the Technician mentioned a new router makes me think maybe he was seeing some kind of network problem in the home causing the problem? If nothing else, if we bypass the router and still see the problem, it will save us having to troubleshoot difficult router settings.
Second, what are the signal levels of your modem? Typically you can find them at 192.168.100.1 website. If this doesn't work, please respond with the modem's model number(usually printed on sticker on modem) and I can give more specific instructions.
Last, what test are you doing, or what data are you referring to when you saying your getting those speeds? Are you looking at download speeds? A speedtest site? Etc.