Frontier Airlines Cancelation policy states within 24 hrs and refund will be issued. They kept my money. unknown unknown

I lost two family members in the matter of days. I booked with Frontier and despite the fact that the flights were pretty awful, I needed to travel to the funeral services. There was a date/time change so within hours, I canceled. They refused to refund my credit card in the full amount and instead offered travel vouchers. Now... I do not travel unless it's for something like this sad situation, so a travel voucher good for a lousy 6 months is of absolutely no use to me. I'm sure this is how they try to circumvent the legality issues. I fought with them via Facebook messenger and that netted me $128 out of the total of $518.96. This is not sufficient and it is not agreeable to me. So, I'm here hoping that someone (gee... 76 complaints as soon as you type in their Airline name) is game for a class action suit. I'm a senior and am far from flush with cash and I'm tired of dealing with shady companies like Frontier. Should I have shopped around? Sure. I did to an extent but with a time sensitive situation like mine, well... you get the drift. I'm sure my situation is not unique. In my personal opinion, they are vultures and prey upon vulnerable people.