They will inform you of your rights and tell you what to do next.

Generally you need to register a grievance with the company and wait 28 days for resolution. If it is not resolved, then it depends on the form and value of grievance as to how it would proceed. In your example of BMW, for example, as it is below 5000 it would likely be a small claim (which would probably cost around 200 to file - the fee is charged by your jurisdiction so will vary - and you would claim the money back as part of the judgement if you win).

But I would recommend just contacting ECC-NET and doing what they say.