The other thing to try is to swap your SIMs and see if that makes a difference. You currently have the 3 SIM in slot 1, which is currently enabled for 3g, whereas the Phone Co-op SIM is in the second slot, which is only capable of 2g. It could be that Phone Co-op's network doesn't support non-3g SMS messages. You can change which slot is capable of 3g via the Cellular system settings, or you can merely swap the SIMs and reboot.
@LionelB
Thanks for the feedback.
First, here's an example of using the send-sms script ( with dummy numbers ):
/usr/share/ ofono/scripts/ send-sms /ril_1 6176666666 "dummy message" 0
The other thing to try is to swap your SIMs and see if that makes a difference. You currently have the 3 SIM in slot 1, which is currently enabled for 3g, whereas the Phone Co-op SIM is in the second slot, which is only capable of 2g. It could be that Phone Co-op's network doesn't support non-3g SMS messages. You can change which slot is capable of 3g via the Cellular system settings, or you can merely swap the SIMs and reboot.