Do you have Samsung Galaxy S4 mini ? if yes then be happy because AT&T has just released a new firmware for your device. VoLTE support, once it is installed, your Galaxy S4 mini will be able to make calls over AT&T’s 4G LTE pipeline. In addition to VoLTE support, the update will also enable the ability to make emergency calls to 911 even when there is no SIM card in the phone.
The file could range in size from 102MB to a whopping 595MB. And make sure that you have a sufficient charge on your phone. Considering the possible size of the update, you might want to have the battery charged to at least 50% before you proceed.