Mobile Network disconnects during an incoming call
This is normal if you are using a CDMA carrier, such as Verizon or Sprint.  GSM carriers like AT&amp;T and T-Mobile can allow simultaneous voice and data, but CDMA cannot.  This is supposed to change with LTE devices, although last a checked it wasn't working with all of them on Verizon.  If you have a CDMA 3G only device it won't work.  I'm not positive but I think even with an LTE device on Verizon that supports simultaneous voice and data it still won't work if you are out of LTE coverage area.  I used to work for Verizon until a few months ago and this seemed to be the case.