Downfall

My internet was just upgraded from 25mbps download and 5 upload to 60/25 but when i try to download games or anything else, it doesn't get anywhere near the speed that I am paying for. I get about 8.5mbps download speeds when I download from steam and around the same for any other place I download from, including Blizzard's client, google chrome, etc. I've gotten a new router and modem because my old ones were outdated, tried a new ethernet cable, and tried using wifi instead of an ethernet cable, none of this helped. It's not just an issue with the upgrade that I bought because before I bought the upgrade, my 25mbps download speed was only downloading at 3.5mbps. I have also tried to contact optimum and everything they told me to do didn't help. Optimum support told me that it has to be my computer and i need to contact my computer manufacturer but the same issue happened on my old computer and my friends macbook. If anyone knows a fix for this, please tell me because this has been very frustrating to deal with.