SoftwareSerial data not available
Don't call portone.listen().  That method is only necessary when you have created multiple SoftwareSerial ports.  It specifies which port you are listening to, because only one of them can receive at a time (you can transmit on any of them at any time).  It also empties the receive buffer so that data from one SoftwareSerial port is not mistakenly returned by another.  In your code, this empties the input buffer before checking portone.available().  Surprise, it's always empty!  ;)

Also, don't set the pin mode of the pins used for the SoftwareSerial object.  The pin modes were set during the constructor of portone, which happens before setup.  You're messing with pins that have been "promised" to that library for its own use and control.

As Edgar suggested, you should consider a more-efficient software serial library.  AltSoftSerial is best, but is only available on certain pins.  My NeoSWSerial library is next best, and works on any two pins, but only at 9600, 19200 and 38400.  Both of those libraries can transmit and receive at the same time, unlike SoftwareSerial.  Here is an answer with all the gory details.

And you really should ditch the String class usage.  You obviously know how to use char arrays (aka "C strings").  We can't see the sending() function, but you can probably just print a few pieces instead of building a complete String and printing it:

    portone.print( '+' ); // leading plus sign
    portone.write( (uint8_t *) customerCode, 13 ); // array of bytes, length


It would be better to terminate the character arrays with a zero byte (NUL-termination) in loop so they can be used as a standard C string instead of a byte array:

    customerCode[14] = '\0'; // NUL-terminate the C string


Then you can use the standard C string print in sending:

    portone.print( '+' ); // leading plus sign
    portone.print( customerCode );


Printing the pieces is always more efficient than building a big buffer with all the pieces.  This avoids copying the pieces and needing twice as much RAM. &nbsp;&nbsp;&nbsp;&nbsp;:P