Told OK to make future changes to flight if charges paid

Unable to use original booking for 4 so I was advised I could make a generic booking if I paid the $50 per person charge, then when I know when we wanted to travel I could change the date for no extra fee. They were only $72 tickets so you would question whether it is worthwhile paying the extra $50 anyhow! I paid the charges as I thought I would use them at sometime (within 12 months). Even though I don't need to use them I thought we would have a weekend away so I phoned up only to be told the rules say every change incurs an extra charge. Why the hell would I decide to pay 2 X $50 to save a $72 ticket that I can buy for $69. Doesn't matter how much you complain they have to refer to the rules even if they don't apply them. The main issue is I made the payment relying on advise from Jetstar only to find out that was untrue. I otherwords I was lied to and they will not refund the $200 fee even though it was taken illegally because they gave me wrong information to get the money out of me, rightly or wrongly. I had read the rules but relied on advise from Jetsar which was misleading and incorrect. Don't trust them.