By stating SOS numbers are you referring to GSM predefined numbers in the configurator?
If yes this could be done by using SMS command <setparam>.
In order to clean the list you would have to know how many predefined numbers are saved in the device, each number has its' own ID. For example: If you have entered 3 different numbers, their ID's would be 6000,6001,6002. 6000 would be the number 1 in the list 6001 would be number 2, 6002 would be number 3 and so on.
To clean the list you should user command with this syntax:
If no username and password is used for SMS command authentication, you should use 2 spaces before command "setparam" in the SMS text dialog window:
After each different parameter ID(example- 6000) you should enter symbol :
After symbol : you enter a value of the parameter, for example a number 3706123123123. In your case we leave it blank so it would clean the value. Symbol ; is used to separate different ID's if you are setting up a several parameters at once with one SMS message.
More information about SMS commands can be found here: https://wiki.teltonika.lt/view/FMB125_SMS/GPRS_command_list
ID list of different parameters is found here: https://wiki.teltonika.lt/view/FMB125_Parameter_list