You could try telling them you will cancel the credit card and not pay the last bill unless they reverse the charge.

When it goes to collections, at least in the US, you can tell the collection agency that the charge is in dispute, and they have to leave you alone.

If the bank then puts a ding on your credit report, you can dispute it with the credit reporting agency.

At some point, someone decides this is too much of a waste of time and pays up.

If you go this route, read up on your rights and the exact process.

One early step is sending them a letter via registered mail saying the charge is invalid because you never received the item. That carries more weight than a phone call, and usually routes to a different department. It might solve the problem on your own.

Make sure the letter makes it clear you understand your rights and know what the CFPB is.