TRAVELSTART NOT RESPONDING ON REQUEST AND IMPOSSIBLE TO PHONE THEM

I previously had a complaint about a booking that I want to change due to Lockdown. Travelstart came back and said I can use my booking until December 2021. Last Sunday the travel restrictions were lifted and I sent a request to Travelstart to request to book the flights for the 6-9 August 2021. They came back and said the cost will be +- R3500 per traveller more and I sent them another request to ask to change the dates to 13-15 August 2021. I've sent them 3 requests and no reply yet. I can't understand why can't they just load my fund on my profile so that I can manage my booking myself. That way I can see if I can afford the flights and choose my own flight times Still you can't phone them at all