Mon 2016/02/01 09:45:48 gammu-smsd: SMS sent on device: "/dev/ttyS1" status=500, reference=-1
Mon 2016/02/01 09:45:48 gammu-smsd: Error getting send status of message: Unknown error. (UNKNOWN)
When sending SMS messages modem reports status=500. This error is pretty sure caused by the SIMcard. Please make sure that it is:
2) have SMS service enabled
We suggest to put the SIM into cellphone, and make some calls, send some messages. If this does not help, we suggest contacting mobile operator to check if SMS service is enabled for this card.