See the following Apple articles:
If you want to cancel a subscription from Apple
If you want to cancel a subscription from Apple - Apple Support
If the subscription that you want to cancel is not listed
If you want to cancel a subscription from Apple - Apple Support
If you see "apple.com/bill" on your billing statement
If you see "apple.com/bill" on your billing statement – Apple Support (UK)
You can request a refund* for a purchase that you don't recognize, but you must pay for the purchase first. You can also cancel a subscription if you don't want to continue it.
*You must request the refund within the refund period. Refunds are not guaranteed. For more information, see the Terms & Conditions.
I am now unable to update the payment system to pay for music
See -> Change, add or remove Apple ID payment methods
Change, add or remove Apple ID payment methods – Apple Support (UK)
- Add first the new card, then remove the old one.
Add money to your Apple ID balance
Add money to your Apple ID balance – Apple Support (UK)
If you're still unable to update your payment method, Contact Apple Support.