If you want specific contacts to know you’ve changed numbers on WhatsApp, the messaging app is making it easier for you to let your contacts know. The app now has a new “change number” option you can access through Settings > Account > Change number. This will help you migrate everything from your account info, settings, groups, as well as chats (if you don’t change phones). The groups you’re in will be notified automatically. But as was seen in a beta update, you can let individual contacts know as well. You can opt to let all your contacts know, those you’re chatting with, or a specific group of contacts. No word yet when this feature will leave beta.
Source: Android Police