If a data controller ignores your GDPR request, you can make an access request for how they handled your request.

Just a pro tip if you want to build a case against a data controller: when they ignore your GDPR request, don’t simply send them a reminder. Instead, send them a new Article 15 request demanding records on how your previous request was handled. This way when you build a case against them, you can tack on yet another Article 15 violation when they also ignore your request for information about how they handled your request.

Not that it matters.. the GDPR isn’t really being enforced. When the DPA ignores your complaint, you’re basically stuffed anyway.