I’m waiting on ?230 cashback myself, so hopefully this is an isolated case. The phone number for the place in Tipp is 1850 930 278, if you leave your name and number and the nature of your problem , they will get back to you (next day in my case). Hopefully your problem can be resolved in this manner.
If not Canon are ultimately responsible and you should contact them.
I don’t think Canon are trying to shaft you but I do understand your frustration at the ineptitude of the third party involved