Unhelpful consultant refused to help me.

Hi, i really hope you can help resolve this matter. I booked a flight to Johannesburg from cape town for this morning. Booking Ref: RHLSPN due to unforseen circumstances i missed my flight. The flight departed at 6:20am as per instructions on your website i tried to manage my booking online as there was another flight available just after my flight at a slightly higher price of R720 but the site didn't allow me to make any changes. I tried contacting the customer help desk on the number provided but a automated response said that the help desk only opens at 7. On my way to the airport i finally managed to get hold of a consultant and explained that i tried to manage my booking online without success and that i had been trying to contact the help desk that only opened at 7 and had been holding to speak to a consultant for about 30min on my way to the airport. When i did finally manage to get hold of someone i was told that i was too late and had forfeited my flight. I don't understand why the consultant wouldn't give me the option of paying the difference in fare and the R300 change fee to put me on the very next available flight as it clearly states on your website. The consultant refused to help me even though id been holding for 30 to 40 minutes to be served she refused to exchange my ticket and said i was 2 minutes too late and had missed the window by 2minutes and had to pay for a new ticket. I've sent multiple emails and whatsapps for help in this regard as im still stuck in cape town and need to get back to jhb asap. Still waiting to be assisted. Service is absolutely SHOCKING!