What you might want to consider is limiting ‘background data’ to do this
Settings >Apps > Select app > Mobile data and Wi-Fi > Toggle background data off
On whatsapp for example, this will only bring you notifications when you open the app as there’ll be no data being used when the app is in the background
Or you can set up a data limit but this is phone wide and not app specific
Network & Internet > SIMs > data warning & limit > Set data limit toggle on > set data limit