The OP is almost a month old but just in case...
Sounds like your ISP is talking rubbish.
Reliable speed testing is tricky, but here's what I do (try to do this with a LAN connected device, not wifi - if you can't, then stand close to the access point).
Always do at least 2 or 3 tests after each other to get an average.
1. Speedtest.net to a local server will tell you your speed from your house to your ISP, more-or-less.
2. Speedtest.net to an overseas server will tell you your ISP's speed to the useful Internet, more-or-less.
3. testmy.net will give you another data point in case Speedtest is slow that day. Also they're a really nice speed test system because you can set a bigger download and upload size. Recommend doing that.
4. Stream a Youtube video. See what quality it auto-selects. Let it run for a minute or 2 and see if it ups the quality or not. Do this at different times of the day and night so you know the highest your connection should be able to do.
5. Download a large (minimum 300MB) file using your web browser and watch the reported download speed in the download window. This is surprisingly useful. Especially if it fluctuates. It should be stable.
NB: Use a site with lots of bandwidth, eg. Microsoft, Apple, Steam, Netflix, Google etc.
The Youtube streaming and file downloading will give you a real world test on stuff that no ISP throttles.
Hope that helps someone.