there is a possibility to use script /usr/share/ofono/scripts/offline-modem with parameter /ril_0 which will stop receiving signals from network, so typing in terminal:
/usr/share/ofono/scripts/offline-modem /ril_0
will turn off SIM1 ... and to say B-side as well
/usr/share/ofono/scripts/online-modem /ril_0 will trun it back on
if you want to manipulate SIM2 just use /ril_1 parameter for those scripts