Not willing to pay for a course
This seems less like an academic question than a question of contract law.  Nevertheless, for what it's worth, if you are refusing to pay the amount claimed, then presumably the onus will be on the education-provider to sue you for the money, and establish in court that it is a valid debt.  You will have an opportunity to argue that they failed to provide you with the contracted service and that the substituted service was sub-standard.  Whether or not you have a good case will depend on the details of the matter, the specifics of your agreement with the provider, and the commercial laws of the jurisdiction in which this occurred.

If necessary and affordable, you should seek legal advice (from real commercial lawyers - not random guys on academia.SE).