I'd be interested to know that as well. My niece signed me up to some family group and when the in laws get going they never shut the **** up!
I ****ing text you that already! Open app Press left button on phone press settings notifications It's all in there turn everything to silent.
From the main WhatsApp screen, bring up the App settings, then click on Notifications, you can modify it so you aren't notified.. just means you need to open up the App for any updates.. well, thats how it works on my Andriod powered phone..