Refunds for cancelled concerts

I purchased tickets in November of 2019 through ticket master to attached her buổi hòa nhạc in March of 2020. That buổi hòa nhạc postponed to September of 2020 and then was cancelled. I am trying to get my money back from my purchase and can't seem to successfully obtain my money back. I used same card Ticket master rules state due refund but it never comes. I have requested numerous times. Please advise how to get my money back 393.64 from that cancelled tour.