How Do I Get a New Phone Number for My Smartphone?

These steps apply to both Android smartphones and iPhones.

1. First, delete your account in WhatsApp (and, if applicable, other messenger apps). Otherwise, whoever receives your old number next may gain access to your content.
2. Then uninstall WhatsApp and any other messenger apps. These apps usually notify everyone in your contacts that you have a new number.
3. You may not want to notify everyone and especially not your (ex-)partner yet.
4. Go to your mobile carrier, preferably to a physical store, and tell them that you want to change your number.
5. This usually takes anywhere from a few hours to a few days. Mobile carriers charge different fees for changing a number.
6. You will receive a new SIM card with the new number.
7. Tell the staff at the store that you do not want to be listed in any telephone directory.