Mango poor services

I had a booking for the 20th of September 2020 at 20:00, and they changed it to 15:00 the same date. Although they did notify me via email and sms, the email was under "promotional", for which I didn't receive a notification for, and the true caller app said the sms was a spam. So I missed the fact that they changed the booking. I went to their offices this morning to explain to them the situation and ask if I could maybe just pay a fine for missing the flight and still be able to fly to OR Tambo, but they refused and said I must make a new booking and pay the full price. I am a student and I don't have enough money to afford a new ticket. Also, I was unable to be at the airport for the 15:00pm flight due to personal family reasons. The service I received at the office was unprofessional and unpleasant, leaving me with a predicament. I missed an appointment due to this mess. I hope that Mango won't treat customers the same way in the future.