Gotogate Refunds One Ticket in Full But Withholds Another's Cancellation Fee

We purchased 4 plane tickets with Air China through Gotogate. The PNR number for one part of these tickets is PV2HOY, and for the other part, it's myexee. Our CA114 flight was cancelled by Air China, and as a result, we filed a refund request through Gotogate. For the tickets under the PV2HOY PNR, we received a full refund, including both the ticket fare and the Cancellation Guarantee (Air Help) fee. However, for the tickets under the myexee PNR, only the ticket fare was refunded — the cancellation guarantee fee was not refunded.
We've been waiting for 3 months for this remaining refund, totaling around $172, for the cancellation guarantee fee that hasn't been paid back to us even though the flight was cancelled by the airline. Since the flight cancellation happened not at our request but because the airline cancelled the flight, we believe this fee should be refunded as well.
Throughout this process, I called Gotogate customer service numerous times. Each time, I was told, "Once the refund comes in from Air China, we'll also pay you the cancellation guarantee fee," but despite months passing, no payment has been made and no concrete solution has been offered.
For the reservation under the myexee PNR number, belonging to my flight that was cancelled by Air China, I am requesting an urgent and complete refund of the approximately $172 we paid for the cancellation guarantee, along with the ticket fare.