To whomever is trying to configure the ZTE Blade A7 to work voice/text, use a network app like "Mobile Network Mode" to force it to select different type of network.
1. Go to the app, select "Force Mode"
2. Set Preferred Network Type: either "GSM Auto" or "LTE/UMTS auto"
This should enable you to make voice call or text both incoming & outgoing.
I had success doing this for my CricketWireless. When doing voice call, it switches to 3G mode.
You must setup your regular APN to have 4G LTE enabled.