In addition to the above, I’d suggest taking the complaint above Customer Service level. Try to engage the airline’s owners and directors. Their time is far more valuable than your refund and a persistent attempt to turn your issue into a conversation is likely to result in someone saying "let’s just sort this" so they can get back to the business of running an airline.
Some useful contacts;
VIVA Air CEO William Shaw – https://twitter.com/wnashaw?lang=en
Irelandia Aviation CEO Declan Shaw – https://twitter.com/decfryan/status/1010272106062471168
You might also want to engage them via their twitter account. Complain vocally and link people to it. You’ll typically find that you get a more rapid response because companies are afraid of poor publicity.
If disputing the charge with your card issuer doesn’t work (or maybe even if it does,) you might want to consider filing a consumer complaint against the airline with the U.S. Department of Transportation.
All carriers operating flights to, from, or within the United States are required to have a customer service plan that meets at least the minimum standard of 14 CFR 259.5(b)(4), which says:
Allowing reservations to be held at the quoted fare without payment, or cancelled without penalty, for at least twenty-four hours after the reservation is made if the reservation is made one week or more prior to a flight’s departure;
The Department of Transportation also provides guidance for how airline’s may comply with this requirement. It’s also worth noting that the air carrier must have their policy for complying with this requirement on their website if they sell tickets on their website. Failure to provide such notification is also a violation of this regulation.
If you used a card, dispute it with your card provider, attaching the order and cancellation confirmations as evidence.
Credit:stackoverflow.com‘