Hyper-popular messaging app WhatsApp announced yesterday that it would start sharing some user data — including your phone number — with parent company Facebook. The two companies say the new policy will help you find friends and "improve your Facebook ads and products experiences"
If you don't trust Facebook with your personal information, and don't want your phone number possibly being sold to advertisers, then you should take a look at the link below
Full article: http://www.theverge.com/2016/8/26/12655518/how-to-stop-whatsapp-sharing-phone-number-facebook