I found myself in this predicament where I need to cancel a flight only booking made on BA.com yesterday evening.

I went through the online process - request a voucher was the only available option but I submitted the request anyway, if only to time stamp my request to cancel
I then followed up via the Contact Us form. An acknowledgment has been received.

It’s been impossible to get through on the phone today and I don’t expect this will change in the hours remain.

Is there anything else I should do?