REFUSAL TO CHANGE OR CANCEL TICKET ON SAME DAY

Booked a ticket online yesterday 29/3 @15h06 for my mom of 91 from Jhb to CT, but discovered at 19h08 that ticket was from Lanseria Airport instead of Oliver Tambo. I immediately emailed Travelwings for a change of flight from OT for a later time on same day or any other day, but was told it had to be cancelled/changed before 12h00am on same day 29/3. My email clearly stated my contact details, yet they only contacted my mom (91 and hard of hearing), whose phone was flat after 12 hrs power outage in Benoni. I offered to pay in any difference for the change to Oliver Tambo, or or even a later time from Lanseria on same day, as it is impossible for my sister to get my mom to Lanseria 1-2hrs before flight @1,25 hrs drive in peak traffic from Benoni, yet Travelwings refused!! I am livid and outraged - will never ever use them again!! Most unhelpful supplier! Furthermore, their staff are inaudible/not at all conversant or clear English speaking. This was a dreadful experience on every level!