Hi Pauline,
My ZMAX Pro was driving me crazy doing the same thing. I took it in to the Metro PCS store (where I bought it), and they couldn't fix it. Frustrated, I started scanning forums online. I got a lot of ideas regarding the cause of the problem, and after a short time messing with my settings, I was successful! The message has not come up at all since I did this. Open up Settings on your phone, scroll down to Apps, and open up your phone's apps. Then scroll down to Stock Android and tap it to open. Go down the list to Notifications, and tap to open. Switch all 4 switches to the off position (switch position to left). Back out to home screen. Press power button and select Reboot.