We're very sorry to hear that you've all been experiencing some issues with WhatsApp notification's on your mobile device.
We're in the process of raising this with our network team, and in order to investigate this we just need a few more details.
As some of the details we need are personal to individual users, you'll shortly receive a private message; If you could respond to that message with the details requested we will be able to investigate this further.
Just to update, I have realised this is not just limited to WhatsApp. It appears anything with a notification is affected, including email, WhatsApp, Facebook messenger and others. It appears that the data goes into sleep mode and if you turn mobile data off and on again everything comes through. This is becoming tiresome though.
I have tried my SIM card in 2 other phones and still have this problem so therefore my handset and it's settings are not at fault.