Why does my iPhone notifications not work?

[Nitepunk]

I have an iPhone 6S and this problem has been persisting for a while and I have just had enough. Facetime, Snapchat, Whatsapp, Messages, Twitter all these I have push notifications turned on for yet I don't recieve notifications most of the time. 1 out of every 10 FaceTime calls I will get the notification that I am being called but other than this I don't get anything causing me to miss out on family members calls so we had to compromise. I also miss out on important messages because of Whatsapp and Messages app not sending notifications. I have tried everything pretty much, I am still on 9.3.3 as I have been hesitant about iOS 10 but if I update will iOS 10 fix this? If not what other solutions is there?

 

[popatim]

In my cousin's case, its his carrier (verizon). We tested extensively one day with my iphone 6, his 6+ and my android g5 (on att).