If you are getting Modem status: Unknown or Disconnected, please check modem log.
You can do it in menu Settings -> Sysinfo tab > Gammu log
Thu 2013/11/21 13:30:25 gammu-smsd[2173]: Warning: no code in config when phone might want one!
Thu 2013/11/21 13:30:25 gammu-smsd[2173]: Already hit 0 errors
Thu 2013/11/21 13:30:25 gammu-smsd[2173]: Terminating communication: No error. (NONE[1])
It means that your SIM-card requires PIN code.
Please enter your PIN code in menu Settings -> Maintenance tab nad reboot the device.