The difference between call waiting report disabling (AT+CCWA =
0,1,7) and call waiting service disabling (AT+CCWA = 0,0,7) is that in
the first case the call waiting indication is sent to the device by
network but this last one does not report it to the modem; instead
in the second case the call waiting indication is not generated by
the network. Hence the device results busy to the third party in the
second case, while in the first case a ringing indication is sent to
the third party.