Date Change cost 60% of my ticket ?????

Hello

I took nearly 2 hours to get through to the call center today.

I book a ticket for 5 June to 22 June 2018 from JHB to JFK upon confirmation e-mail I see the dates are now 5 Jun - 22 Jul 2018, I phoned in to change the dates and travelstart wants to charge me R5500 ?

A new ticket costs R9000 I paid R8400 ... I do not know where all the fees and charges come in but to pay 60% of a whole ticket just to change dates by 1 month (which is travelstarts error) I read the negative reviews that cancellations and refunds are worse and people only get 30% of their paid amount back.

I would just like to change the dates to my correct travel dates, if travel start cannot get this done, I want a full refund and I will never book through them again and use other sites instead.