Whatsapp is used by 1 billion around the globe and is one of the major social media apps being used in Pakistan. But being such a major part of social media means spam and irregular use of Whatsapp for marketing and flirting.
To stop it Whatsapp have introduced barriers which can ban users temporarily or permanently forever. Because Whatsapp believes that the app should only be used to connect with your friends, family and colleagues.
So if you send same message to many people on your list then Whatsapp software will consider it spam, if you have to make an announcement then it is better to use broadcast message option.
If you make many groups and add those who are not on your contact list then Whatsapp will also consider it as spam and will ban you.
If after receiving messages from you someone reports you then after investigation your account can be banned.