I was having the exact same problem with the exact same phone and I have found this fix on; http://zte-iqorsupport.custhelp.com. It has seemed to work for me, so far. It has only been a little while since I did this, but so far so good. I hooe this helps y'all.
This type of problem could be due to a conflict between an app and the phone’s operating software. To fix this, one of the best steps is to Clear Cache Partition; however, if you phone does not have this option we would want to do a master reset.
We always advise backing up the phone completely before preforming either step, and our Device Support page has a step-by-step guide to complete this. After selecting your phone’s make and model, please go to Tutorials > Backup & restore > and then choose your preferred backup method.
Once the backup is done, we are ready to move to the next step. If the phone has the ability to do a clear cache partition, you will follow the steps to do the alternate master reset but instead of selecting Factory/Master Reset scroll down to Wipe/Clear Cache Partition > select it with the power key > Reset/Reboot Device.
If you do not see this option on your phone, please go to the Device Support page, and choose Tutorials > Reset device. This will take the phone back to factory settings, and get rid of the conflict.