Make sure when you do speed tests at testmy.net you use the 12MB manual size for downloads and the 2MB manual size for uploads. It would also be a good idea to create an account at testmy.net and do your tests under that account so it can keep a running tally of tests in case your speed needs to be addressed by the reps in the future.
Also, make sure that you are connected directly to the modem when doing speed tests. No router.
If you have Windows 10, your system might be updating as some updates were just released sometime yesterday.