Are you already logged in to another device? Then you can look up your user name for myCloud under "Settings".
Otherwise you can renew your login credentials (username/password) here.
Choose between “Forgotten password” or “Forgotten your username”.
If you’ve forgotten your password, enter in your Swisscom username. You’ll then receive an email with an identification code. Enter the code in the corresponding field on the website. Afterwards you’ll be able to create a new password.
If you’ve forgotten your username, you’ll need to enter your email address or phone number. Your username will then be shown after you enter in the identification code.