If your phone is lost or stolen, use "Find My iPhone" to lock it. You can then protect it with a new password or by remotely deleting your personal data.
In addition, you can always temporarily block your card by logging in to your Paysera account or by calling Client Support.
However if you lose your device or if it is stolen, please suspend/delete token through iCloud immediately. If you are unable to access your iCloud, place a request with client support to suspend/delete the token.