Poor service provider

Travelwings poor service provider i called today coz i wanted to do a rebooking on my flight first before cancelling my flight i paid R2900 then i place my ticket on open coz something came up now i want to resume my flight on the email they sent me it states that Airline rebooking is R500 and agent fee us R300 Total R800 then i checked on their website the cheapest flight is R4522 then im supoz to pay the difference plus R800 thats what the email says but No the have a different portal they use for rebooking now it calculates that im supoz to do my rebooking and pay R7000 thats tripple the amount i paid first thats not a difference and thats day light ******* refund me or rebook my flight pliz