Booking blues, terrible service

I initially booked a return flight for the 5th of June 2019 on the 8th of May 2019, through Kulula.com's website. I payed the required amount with my cheque card, and the amount was immediately credited from my account. I didn't think much of it, and regarded my flight as being booked. When I looked for the confirmation mail on the 30th of May 2019, I couldn't find it. I tried Kulula's helpdesk, which informed me that my booking hadn't been made, and that I should merely "book another flight". This is a terrible and unhelpful solution to my problem, as we all know flight become exponentially more expensive closer to the date of the flight. I received no notification that my flight hadn't been booked, and the site explicitly stipulates that a cheque card is an accepted form of payment. After booking, the site had informed me that my booking had been made.