How can I get money back from refunds paid to a closed credit card?

HSBC have not sent me a cheque, nor have they refunded me through my bank account. What should happen in this situation and how can I get them to give me my money back? https://www.dailymail.co.uk/money/experts/article-9266651/How-money-refunds-paid-closed-credit-card.html?ns_mchannel=rss&ns_campaign=1490&ito=1490