Bad service

Booked a flight on 03 May afternoon using the FlySafair App, to fly out of King Shaka Int'l Airport on 04 May @13h55 to Cape Town Int'l Airport. Booking was successful after several attempts and funds (R970.57) were deducted off my account. However, I didn't get a confirmatory e-mail with a Booking Reference, meaning I couldn't check in online. Contacted their Contact Centre, but couldn't get through (as they also had a 30% sale that day and next day). tried it whole night until Contact Centre closed, and the next morning (04 May) I tried getting thru the Contact Centre without much success. eventually sent someone to FlySafair Sales Counter at King Shaka to check on my flight booking, and he was told that my flight wasn't booked but the lady at the counter could only see two failed attempts. Solution was that I must book another flight, which I promptly did and seaty on same flight (13h55) cost me R1431 as it was now closer to flying time. I then departed on that flight at a higher cost, and when I arrived at Cape Town Int'l Airport I went to FlySafair Sales Counter to query my earlier flight I paid for (on 03 May). Again the lady at that Sales Counter also couldn't see my flight, but this time could see three failed attempts. I showed her the message from my banking app clearly showing that I paid for a Flysafair ticket at R970.57. She then suggested I should call the Contact Centre again as they are the only people that could assist. On 05 May (morning), I contacted the FlySafair Contact Centre and spoke to a Ms Mabaso, who confirmed that she could see my flight that I paid for (i.e. the one that couldnt be seen by the two people at their Sales Counter - Durban and Cape Town) and she suggested that it could have been a system issue related to the 30% ticket sales. I then told her that I was inconvenienced by FlySafair system and was forced to purchase another seat on the flight at a higher cost, and therefore require a refund of my second ticket (i.e. R1431) as I reasoned that I wouldnt have purchased the second ticket (at higher cost) had my first ticket been honoured by FlySafair. To which she concurred and said she will escalate to her Manager. I also put all this down on e-mail to Ms Mabaso, but did not receive a response yet. Today, I called the Contact Centre again, and relayed my story and that I need a refund on the higher cost ticket. The gentleman that assisted me again concurred with my view and escalated the matter (the call was dropped, which meant I had to call back twice) and when he eventually came back to me, he told me they will refund me with a voucher. I told him I do not want a voucher but my cash because I dint voluntarily cancel my ticket for any other reason. It was FlySafair's fault that I had to book another ticket and therefore have put me out of pocket. So they cannot tell me about their voucher refund policy! I will not accept that !!