I once did some work at an insurance company and they had some systems problems slowing down payouts etc. There was a room full of people specifically tasked with fobbing off clients. The magic words were, "I want to make an official complaint." They now had 48 hours to fix the problem or they had to register the complaint with the regulator... and they didn't want that to happen. If that happened you were passed to a professional complaint handler who would move heaven and earth to get things settled before then.

I have since managed to change the tone of several conversations to regulated industries with that phrase!

Now make a GDPR request at the same time... that seems to get you answers too