Answer: You can use <AT+CSNS=4> to answer only data call, an incoming voice call will be refused automatically…
But no impact on outgoing data/voice calls. You can still make an outgoing data/voice call.
For example:
AT+CSNS=4 —Incoming data call can be accept, Incoming voice call will be refused automatically
OK
+CRING: REL ASYNC
ATA
OK
…
AT+CSNS=0 —Incoming data call and voice call are possible to accept.
OK
+CRING: VOICE
ATA
OK
…
+CRING: REL ASYNC
ATA
CONNECT 9600
OK