Wrong invoicing and no help afterwards

I ordered an e3 flasher from Gaming Mods N Repairs PTY LTD, I paid what was invoiced to me, but now there is still $24 (AUD) missing. I have spoken to their support team but they have not responded to my latest inquiry for over a week now. If I am suppose to pay their bank charges for International TT they should put it in the invoice so that I know the exact amount to place into their account. They invoiced me for $67.50 (AUD) and that is the amount I placed into their account. They have not processed my order for I still owe $24 (AUD) in their books, they haven't shown or explained to me where that money disappeared to or why i should pay it, therefore I decided to up the game now.