I'm far from an expert on L3-L2 ISPs and their tech, but they usually rent the line from whoever owns it and then sell it back to you - then they cap the speed between you and the box.

It's most likely an operational mistake - have you called and asked for them to nuke the line and then set it up again?

Or are you saying that you are getting your advertised speeds, and those just didn't go up when you "got fiber"?

Don't know which one is more worrying if true, to be honest.