Flapp App Service Sucks

I booked a ticket for a friend and due to it being Xmas, tickets are at a premium. Whilst booking I filled the passenger and banking details only for the app to note that the flight had already been booked. So, fearing losing out on the next best flight, I booked that as well, only for both flights now booked. I had immediately tried to contact them, but the only option is WhatsApp, which they haven't answered. Or, the cancelation which I keep clicking on because it seems to disappear every couple of hours, without any interaction from anyone at Flapp. Please can someone assist, because prices during this time aren't the cheapest and I need to get recompensed.