I've tried it, a dozen times, in two European countries with, on paper, strong data protection laws. Every single time, after anemic back-and-forth, the national data protection agency basically told me "they say it's fine and you opted in, nothing we can do".

Sometimes you really hit a dead end. Some orgs just don't respond, or say they don't have the resources to process your complaint, or lie. The codified consumer protection laws are nice, in principle. Multinationals know they can get away with pretty much anything.