vvizo all touch customers on WhatsApp bundle have this problem.
Maybe they're blocking or breaking GCP for push notification.
You can capture the traffic, PCAPdroid makes this incredibly easy, just click the play button without changing anything.
Port 5228 is for GCM and is used to for push notification messages or wakeup apps that depend on it like Whatsapp (due to encryption), 5229 and 5230 are backup.
The connection stays open even with the screen off, you should rarely see it being closed and reopened.
There is a log with timestamp and and convenient filter like in this example to track closed connections with port 5228:
Closed and reopened from switching from Wi-Fi to mobile.
I hope they didn't block it because of notifications from other apps, since it's whatsapp bundle only, that would be funny.
Unlike Whatsapp, if they were to add Signal, it will fall back to Signal server from GCM, but it requires setting the app to be set as unrestricted in battery settings and will cause battery drain.
Social data covers more apps, worth a try: https://www.touch.com.lb/autoforms/portal/touch/personal/prepaid/magic/bundles/socialdata
