I got burned by Ryanair at the start of the pandemic. I'd paid something like £2,000 for flights, and for months those scumbags refused to refund me.
I'd paid with a credit card, so I asked my card provider to do either a chargeback or section 75 (I forget which) to force a refund, and the money was back in my account within a couple of weeks.
I had a hotel double charge me a number of years back. I called the hotel to straighten it out and got some run around. So, I called my bank (USAA) to ask what I should do. They said “do a chargeback and that’ll force them to show documentation”. “Okay, I’d like to chargeback one of the transactions.” “We’ll just do it for both and let them sort it out.” Hotel never responded at all, so the entire stay was free instead of just being the correct amount.