ZTE Blade Spark will not display incoming call on screen - ONLY shows a notification

Really disappointed with the lack of responses to the past posts about incoming call displays not showing up on this phone.

Nothing indicates or solves why the phone will not display an incoming call. I have to swipe down on the notification bar and then click that an incoming call is occurring. The only reason I would know that there was a call is because the phone rings. Really baffling how this could even be something ingrained into the software of the phone and is impossible to change. I have gone through every trouble shooting topic possible on AT&T troubleshooting and resolve page. 

I should not have to take my phone in or try to call a help center to figure out how to display a receiving call...literally the one thing the phone should be able to do naturally...