In many legal jurisdictions, a 'demand letter' holds weight. These can be served by courier, with proof of delivery as valid. One aspect of such a letter is a hard, specific time by which you will start legal action, along with associated additional costs.
You have two paths after the letter. The first is small claims court, or normal court. In many places, small claims court does not allow lawyers, and the judge will even have to explain any confusing terms.
Which means the playing is leveled, including reduced or no disclosure requirements, and legal cost assignments. Where I am, it's $100 to file.
The goal is to force a fix, at threat of legal consequences.
I am sending an email.
You would be better off in the US. Trust me, nothing creates bigger fuzz than complaining to financial authorities.