When I upgraded a subscription, there was a refund automatically received on my account in about 4 days without me having to do anything. Not sure why you are having trouble contacting Apple directly. I am guessing from your username that you may be from New Zealand and there is a live support phone number for you. Some regions have hours of operation on their support line, but for most, it really is not that difficult. If you are not from New Zealand, you can choose your region for support options and confirm with them that you are getting a refund.
Contact Apple Support - Apple Support
Also YouTube offers a subscription in their app that is managed by Apple and on their website where it is YouTube that manages the subscription. It is possible to see a double charge when you have a subscription from both platforms or choose an upgrade on the other platform. Stick with the same platform for you subscription, or cancel from one platform if you want the other to manage your subscription.