WhatsApp is one of the easiest way for instant messaging. But people did encounter a major problem when they have to move from old phone to a new phone. This is difficult to keep messages intact because the content is saved locally and no on web servers. So if you are switching, iCloud could be the one option that helps you to back up and then restore your messages smoothly. For iPhone, this is the best way to create back up and then restore Chat.  

1. In order to create backup firstly you need to go to Settings, Chat, Chat Backup, and then click Backup Now.
2. Once you are on a new handset, confirm your number and you will prompted to receive your Chat History.
3. Tap Agree and your Backup is restored.
4. You can also go back to the settings and enable the Auto Backup feature for the next Back up.

So now you will have enough to save when switching to a new iPhone.