Happened to me with Alitalia once, they changed their stance immediately when I put the local office of civil aviation on Cc: and the money was soon in my bank account.

This is the trick. The CC'd address doesn't even have to be correct, just make sure the host/domain part is the correct official local authority, and they'll do your right really quickly.

They almost always try that. Save yourself the hassle, use one of the online services who will get that money for you.

Plenty of frequent flyers are willing to help for free too (I assume a majority of those services take a cut). FlyerTalk, Head For Points forums etc

How far have you taken it? Letter-before-action mentioning CEDR/MCOL? (The stage at which European airlines begin to consider stopping their blanket "no" response)

Switzerland might have options for small claims court claims online too

Have you filed a complaint with the swiss air regulatory authority? I did that when Icelandair didn't comply within the allowed timeframe and suddenly they were much more forthcoming.

Had a cancelled flight with Swiss which they claimed was birdstrike and hence force majeur. So no compensation …