I was curious about IDEAL as well, this help file (here: https://www.ideal.nl/en/consumers/) makes it clear that you don't raise the problem with either Qatar or the Bank, but with the "iDEAL contract party", which is one of these companies and are essentially the third party payments processors: https://www.ideal.nl/en/partners/acquirers-and-cpsps/
If that has been done then I guess all you can do, if Qatar fails to respond to an in-writing request, is start court action. I suspect that many will be confused since this looks to be fairly popular in one country (Netherlands) but is different than the typical payment method and process where you would go back to your bank, hence confusion here too.