How to pauze WhatsApp from retrieving new messages? - Data Saver-function stopped working!

[Xperia Z5 Compact-user]

Data Saver-function stopped working for WhatsApp since I updated my Z5 compact to Android 7.1. Very annoying. Nothing can stop this app from using background data: not the 'Data saver' option anymore; not turning off the 'auto-sync' option; not the special Sony 'stamina' mode (that should kill background processes). I did find though that the combination of turning off 'data saver' option and turning on the Sony 'stamina' mode brought about a bit of a delay in receiving messages, about a minute or 2... so that's still useless.
During the evening/night I don't want to automatically receive messages, even when I have my phone in 'Do not disturb' mode. I want to be able to look on my phone and have no notifications coming up (at all! - no icon, no light, no nothing), and have that function easily turned on and off, without having to scroll down menu's and manually kill notifications for just the WhatsApp-app (and still the app shows in the icon the number of unread messages you have). 'Data saver' option did just that for me, but not anymore.
You could say, turn off wifi and mobile data all together, but I think its handy to be able to go online even without having all these messages being thrown in my face... I want a bit more peace of mind

Any suggestions? Thanks a lot!

 

[B. Diddy]

Moved to the WhatsApp forum.