applying apple gift card to my apple iD account
I tried to link an apple gift card to my Apple ID...not to buy something now, but to have it show as a credit for later use. The system charged my credit card instead. I've searched help topics and looked for "contact us" info - no luck. Anybody know: 1. how I can get a credit card refund, and 2. how I correctly apply apple gift cards to my account, as a credit for later use?
MacBook Pro 13″, macOS 10.12