Sepura tetra SGR 3900 AT command

[pesch]

Hii I am newbie and still learn to using AT command in sepura tetra..
I have trouble about get SDS in this device..
I tried to using AT+CMGL and AT+CMGR to get SDS data the return code +CME=3 or "operations is not allowed", what can I do to get sds message in this device?

Many regards,
Zokypesch