Mango unwilling to assist a elderly person

This will be the first time I complain publicly on social media. I booked my mother - 84 years old - on a mango airline flight from OR Tambo to Cape Town. The flight departure at 9:40. Due to heavy rains and traffic in Pretoria my mom phoned me saying that they not going to make it. I phoned Mango explaining the situation. Ronald Cloete team leader at the call centre stated that can move her to the next flight at a additional cost of R 2309.20 in my opinion if there is space available on the next flight why the ridiculous addsional charges?. Mango Airlines and their staff was totally unwilling to assist a elderly person. Sham on them