Absolutely ****!!! Bad service & help!

Absolutely sh*t!!! I paid a lot of money for a flexi ticket from south africa to canada and back and now I need to use my flexi ticket to change dates and the gotogate colsultant first said there js no flight available for the 5 new dates I have him and then he said its going to be R7200 is I want to change it ? What is the point of buying a flexi ticket?