The most important piece of information that is missing here:
How long ago you cancelled the product??
Sometimes it may take upto 7 to 10 working days.
Please wait until such time.. you will get your refund for sure . because everything is automated these days..
Otherwise you can raise a ticket for that particulaer order by hitting " Need Help?" link..
A ticket will be raised and someone will answer you and call you if needed.. You can also talk to CC guys via this Help link..
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BEst wishes