I know you can dispute charges once posted. But can I prevent my card from being charged by a specific merchant -- short of getting a new card number?

The backstory is I ordered something 2 months ago. It hasn't shipped, despite the quote of delivery in 5 days from the time I placed my order. (n.b., 2 months ago was pre-quarantine.) I called the retailer to cancel my order, but they said the order is processing and cannot be cancelled.

The silver lining is they haven't charged my card yet. How can I block that?