Never wait to file a chargeback with your card issuer if a refund is due and denied or delayed.
Make certain that you do everything in writing (including email and webforms) and that you supply the backup documentation with your chargeback. When your chargeback package is complete, there is little to nothing the vendor (carrier) can do and its merchant acquirer is unlikely to waste any effort contesting the chargeback.
FI is an EU carrier. It is subject to EC 261/2004 and Section 8 requires that a refund be initiated within 7 days when the carrier cancels or significantly changes a flight. Your package should include a copy of Section 8, along with your e-ticket receipt, your request for a refund and any response from the carrier. No reason to wait beyond the 8th day.
Similarly, if your flight is not cancelled, but you do not wish to / cannot travel, do not cancel yourself. Wait until the day of the flight. It may well be cancelled or changed. There may be bad weather or a mechanical issue. All of those entitle you to a refund. If there is not, then go ahead and cancel and take the "funny money" credit voucher.