For cash-paid tickets, just wait a reasonable period of time and then initiate a chargeback with your credit card issuer (bank). The easier you make the package you submit, the better,. Include your e-ticket receipt, the cancellation notice, your request for a refund and either denial or a note that you have not heard back. Be sure to keep copies or screenshots of everything (no different than any other transaction).

If your ticket included segments departing the EU, then EC 261/2004 requires a refund be initiated within 7 days. If your ticket included segments to or from the US, then US DOT rules require a refund be initiated within 7 days. Thus, a chargeback for those tickets is certainly in order on the 8th day.

No need to waste time chasing AC and spending time on the phone.