If you subscribed through YouTube TV, you will need to log into the YouTube TV site or use YouTube TV-related apps/devices to manage your subscription, you'll also need to log in to your YouTube TV account to make changes.

To manage your payment methods:

1. Click on your profile picture. 
2. Select Settings à  Billing .  
3. Click Update next to "Payment Method" to view your current form of payment, change your form of payment, or add a new form of payment.
4. View your order history. Click View next to any charges to see more details.