30 days is a period for a product full refund, not for a double credit card charge. If they took your money by mistake they must return them regadless when you notified them, 30 days later or a year later.
Maybe you just tried to trick them by buying CMUD, using it for a month and then asking for refund?

Anyway, I highly doubt that they would steal money from credit cards AND not return them even when caught.