The code arrived but does not work. Can I get a refund?

Once a message has been delivered, the number counts as used and is not refunded, because the service did send the code. While the timer is still running you can usually fix it: ask the service to send a new code, which arrives on the same number, and enter the newest one. Check that you are entering it in the right app and before it expires there. See Receiving more than one code.