Great question — answering as the UphillTech team:
This is unfortunate and one of the reasons why you should always book with the airline directly. A lot of governmental protections, such as the US 24 hour free cancellation rule does NOT apply to 3rd party booking agents. Mytrip.com has a large number of negative online reviews so chances are they will not relent and try to hold on to you money if they can. Your best option is to work with your credit card company: document the interactions and let them know that Mytrip.com has no way of delivering what you have purchased. Ask them what specific documentation they need to see to execute the charge back. The fact that the airline has already refunded the money back to mytrip should help...
Full answer by Hilmar: https://travel.stackexchange.com/a/195619 (CC BY-SA 4.0).
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