You can update your card details during the renewal process. Because your subscription is on auto-renew, the auto-renewal feature must be disabled first. You do this as follows:
Go via Music to Subscriptions in the left-hand column
Press the pencil next to the zone name
Click the On/Off checkmark of "Renew automatically" and then 'Save'.
After that, you can renew your subscription and change your card details as follows:
Go via Music to Subscriptions in the left-hand column
Press renew
Follow the instructions on your screen