iphone – I don’t receive calls or messages from messenger or Instagram or Skype..etc even though I’m online


I’m using iPhone 6, I have a problem recently, I don’t get any calls or messages from messenger or Instagram and the other apps, even though the WiFi is on, and the person who calls, it appears to him that I’m offline, and if they send a message it Will be just sent not delivered, untill I open the app, they can call me, but the other apps Will be offline, so how can I fix that?