
Change the privacy settings of WhatsApp messaging to prevent unknown numbers from adding you to chat groups without your permission.
WhatsApp is one of the most widely used mobile messaging systems in the world. Besides the possibility of sending messages at no additional cost, regardless of the country in which your loved ones are located, WhatsApp is extremely practical to manage creating group chats.
But sometimes we find ourselves invited to discussion groups of complete strangers without really knowing why. However, it is possible to restrict invitations to group conversations to only contacts in your address book.
1. Open App Settings
Launch WhatsApp and go to the Settings of the app. Then enter the Account menu and access the Privacy options.

2. Allow groups for your contacts only
Then enter the Groups menu, and change the default setting, Everyone (which allows any WhatsApp user with your number to add you to a group conversation), to My contacts, or My contacts except …

If you choose this second option, you will be prompted to select the contacts from your address book that you want to prevent from adding you to group conversations without your consent.