OK there may be a better way to do this, but I'd look up the c++ references for "strtok", and the related "strtok_r"
Essentially you feed it a string, and tell it what characters separate different fields within that string. It returns the first section of that string up to the first delimiter, and chops that bit (and the delimiter) off your original string
You'd set up a quotation mark as the delimiter, then feed it your string, and throw away the first result (it would have everything up to the first quotation mark). Feed it your string again, and it'll return your phone number.
This is a really common thing to use for GPS applications, where you parse a NMEA string to get out the variables such as longitude and latitude from a single string. Here's and excerpt from my GPS parser (pretty much copied from the diydrones code)
void altitude2_parse(void){
char *token; // this is the new string that will contain the chopped off bit
const char delimiters[] = "$,"; // these are the delimiters
token = strtok_r(altitude_buffer, delimiters, &brkb);//token contains just the header string "GPGGA"
token = strtok_r(NULL, delimiters, &brkb);// now it contains the UTC time
time=atoi(token); // convert the string containing the time to a variable
... //etc
}