If you already have a dongle that doesn't do CAN bus, how do you think it will be able to do CAN bus?

What you have now sounds like OBD-II only. Different tools can get more info from the same connections. e.g. my BMW can have a generic reader attached to get the legally mandated stuff via OBD-II but with specialised tools and interfaces lets you get into all the custom stuff like seat memory, lock while driving etc.

What car? Is there a CAN bus connection on the OBD-II port that you know of? Should be pins 6 and 14. If something like a VW/Seat/Skoda/Audi/etc there are specific tools and interfaces to look at. e.g.
http://www.ross-tech.com/vcds/canbus.html

Unless you just want to look at raw CAN?