No refund since June for deceased son

Our son died in May 2021. We had booked a flight for him to fly with us on holiday in July 2021. He was obviously unable to take this flight and we have been fighting with British Airways/Comair since June 2021 for a refund of his ticket. We have sent e-mails which go unanswered, made calls that require you to hold for over an hour before anybody bothers to pick up the phone, only to be made promises that go unfulfilled and with no follow up. We have lodged formal complaints directly with BA, only to be told they cannot help us and we must go back to Comair. We are at our wits end as to how to get the refund for our deceased's son ticket. The service has been disgusting to say the least.