WhatsApp changes things. You do not need a phone number soon. You choose a user name. This keeps your private life safe. You keep your number secret from strangers.
You can pick your name now. Open your settings. Look for the account menu. Select the option for user name. You can use names from other apps. A name needs 3 to 35 letters.
Apple users get this first. Some Android users wait longer. WhatsApp adds the feature slowly. A message shows when you can start.
There is no public list of names. You must know the exact name. Then you start a chat. There is a secret code with numbers. It stops messages from strangers.