TRYING TO USE JETSTAR VOUCHERS TO BOOK FLIGHTS

Yes I made the grave error of getting a Jetstar Mastercard last year - the rewards are in Jetstar vouchers - their customer service does answer but you get absolutely no where.
On initial use of the card you are supposed to get a $200 voucher - well this didnt happen, numerous phone calls and 3 months later I finally got that voucher shortly followed by another voucher for accumulating points.
The fun then begins in trying to use them - put the voucher into the booking online and get - voucher number not valid - then I try by phone - its expired - the dates clearly state 3 months to book and travel within 6 months and I am within 3 months of the date of issue - 2 hours on the phone and its elevated to a complaint, follow up 2 days later with another 30 min ph call to be told by the "customer service" operator that she can make a note to call me EVERY FRIDAY till its resolved. YOU HAVE TO BE JOKING JETSTAR. I got the impression that it could be months - well that would indeed be one way of making sure vouchers are expired before they can be used.
How do I solve this problem - simple - cancel the credit card and travel with other airlines from now on, I have better things to do than spend hours on the phone getting nowhere, especially after reading other posts on this site.