This.

Do not waste your time arguing with front line clerical personnel who have no say or capability to do what they have been instructed not to do.

Request the refund, keep a screen shot of everything and download the policy showing that the reservation is now refundable and then give it a fair period of time. DOT provides air carriers 7 days and that seems reasonable here. On the 8th day, file a chargeback. Submit the policy and screen shots.

This both puts the shoe on the other foot and protects you.