To Update or Change your Billing Information
If you subscribed through the Strava website, you can manage your billing method from the Settings page. Click on your profile picture in the upper right-hand corner and select Settings from the drop-down menu. Click on the My Account tab on the left side of the page. Select the option to Update or Add Payment Details depending on whether your subscription is set to automatically renew.
If you see the option to Manage your subscription in Google Play or Manage your Apple subscription on this page instead, you'll need to manage the billing information you have on file in the Google Play or iTunes store respectively.