Don't know what library you're using, but at https://github.com/adafruit/Adafruit_FONA, FONAPlatStd.h has the typedef:
typedef const __FlashStringHelper *FONAFlashStringPtr;
That's not the same as:
typedef const char* FONAFlashStringPtr;
Don't know what library you're using, but at https://github.com/adafruit/Adafruit_FONA, FONAPlatStd.h has the typedef:
typedef const __FlashStringHelper *FONAFlashStringPtr;
That's not the same as:
typedef const char* FONAFlashStringPtr;