I booked 2 tickets to AKL mid March and cancelled within the 24hrs and got the refund within 10/12 days.

A few days after, the airline cancelled three tickets(bookings made in Jan/Feb) and l asked the reimbursement, but so far no news.
When should I consider starting a charge back from the credit card company?
I don’t mind waiting another 3/4 weeks but would not like having to wait until December or so.

Thanks,