I don't think the CC dispute will work. You can claim any number of reasons that you decided to change the flight, and that the airline didn't satisfy your reason. But that's not what controls a contract between you and the airline.
Chargebacks often work when they "shouldn't", because it's more hassle to contest it than to just give you your money back. But one of the reasons for chargeback is that you never received what you paid for, and that's pretty applicable here. Ultimately, your advantage is that it's in the hands of the credit card company, which prefers to make you happy if possible, rather than in the sole discretion of the party that would have to pay you.