Have the cards actually been charged? Most likely the transactions are just pre-authorisations which will age off.
If you have actually been charged then you need to contact the card issuers and request a chargeback for each transaction, neither Visa or MasterCard have any involvement.
Also... VietJet don't appear to fly between Hanoi and Hue and flights should be changeable for a fee. Are you booking direct through the official website (vietjetair.com) or an agent?