The definition of net neutrality is (from wikipedia):
Net neutrality is the principle that Internet service providers and governments regulating the Internet should treat all data on the Internet the same, not discriminating or charging differentially by user, content, website, platform, application, type of attached equipment, or mode of communication
The issue is that Videotron in Quebec was not counting a certain streaming service’s data usage against customer’s data cap. This meant if you streamed 300mb of data from the service, it would not count against your 4gb data plan, but if you used a competing service it would count.
That is a direct attack on net neutrality, where an ISP or mobile network provider is directly favouring one service over another, which distorts the free market. We will see today what the CRTC has to say about it.