Gotogate Delays My Refund a Month After the Airline Confirmed Cancellation

I purchased a plane ticket through Gotogate for a June 14th Athens–Istanbul flight, with reservation code 1113-533-070. About a month ago, the airline sent an email stating that the flight had been cancelled and that the ticket fare would be refunded.
Even though I made the total payment of $161 by credit card, a month has passed and I still haven't received any refund. I had to struggle for a long time to reach Gotogate about this matter — despite spending nearly 2 hours on the communication process, no concrete solution was offered and no refund was issued.
I am requesting that my $161 ticket fare — which the airline has already confirmed for cancellation but which still hasn't been reflected back to me — be deposited into my credit card in full as soon as possible, and that the process be communicated to me clearly and in writing.