Try the below script in the AT Command Tester tool
//Script: at+cfsgfrs - Get the free size of file system //The AT commands in this script are applicable for Simcom modules only //Check SIMCOM Module AT Command documentation //Get the support for the commands AT+CFSGFRS?
Output of the above script in the AT Command Tester tool
AT+CFSGFRS? +CFSGFRS: 5836800 OK