Ticket cancelled after confirmation received

On the morning of the 23/04/2019 I made a reservation for my mom in-law from Cape Town to Kimberley. I contacted the office to make the booking and have the option to pay later because I was at work at the time and did not have my bank cards with me . The person I spoke to told me that I must pay within 72 hours. I arranged for a wheelchair and the lady told me to call back after 3 hrs to confirm if it was arranged. When I called back after 3 hrs and gave my ticket reference no, my ticket was cancelled despite the arrangements I made earlier and I had to rebook the ticket at a higher price.