Adding SOS number to GPS personal trackcing device

[Govind]

Hello, I use Personal GPS Tracking Device Model : GK309E 2nd Generation GPS Students Phone.

1) When I try yo add SOS number via SMS command :

SOS,A,944870160760#

I receive the following SMS error message : "Error! Only SOS phone numbers are allowed to set".

Could you please help me, how to solve this error?