Cancelled flight

In September 2024 I booked 3 tickets, 1 from Johannesburg to Umtata and 2 from Umtata to Johannesburg costing a total of R7 164. The flight was SA Airlink but I booked the tickets via Travelstart. The trip was to take place on the 20th of September and to return on the 22nd September. I arrived on the 20th and waited as the flight was delayed. Eventually the flights for that day were cancelled completely due to bad weather. SA Airlink offered an option of a refund or using the ticket to book a flight on a different day. I contacted SA Airlink for my refund and they informed me that due to my booking done via Travelstart I need to direct my refund request to them. Travelstart declined to refund for these tickets even though the airline was prepared to give a refund or a voucher. How come Travelstart has different rules than those of the airline? Does this mean in order not to be disavantaged I need to book directly with the airlines and never book with Travelstart?