I feel cheated

We had a family crisis and I had to change the tickets. I called to change the tickets on parents' behalf (they are pensioners and are obviously not drowning in money). With the penalties involved, buying brand new tickets would have been only R300 more. When I wanted to cancel the change - while still online - the lady told me it could not have been done as the tickets that we have already paid for - has been sold (in the 1 minute that I was on the phone with her) and I had no choice but to buy the new tickets. Never was the process properly explained. I feel very muich done in and actually as if we have been ******. Shame on you Kulula.