WhatsApp makes use of machine based algorithms to decide whether to ban a
number. They do such checks at registration, as well as during the
number’s WhatsApp activity.
We suggest the following tips to avoid getting banned:
1. Do not use "WhatsApp Plus" or "GB WhatsApp" or any other 3rd party client. This will most certainly get you banned.
2. If you previously got banned, attempting to verify additional numbers
from the same network connection will very likely to get you banned
again. Change your network connection (e.g. WiFi to cellular data or
vice-versa) for future verification.
3. If you just activated a new account, you should avoid the following:
a) Sending too many messages to users who aren’t in your address book.
b) Being blocked by too many people in too short a period.
c) Creating multiple groups containing users not in their address books