Error using matlab for messaging with huawei modem

I am using Huawei E3531 model for sending message by interfacing it with matlab. But it always shows an error. Do I need to unlock my Huawei dongle?

If not, what is the actual problem? I am using the following code:

clc;
clear all;
global BytesAvail;
global A;
global B;
tx ='ATI';
tx1=char(13);
tx2=char(26);
tx3='AT+CMGS="[phone]"'; 
tx4= ' This is a test msg ';     
tx5='AT+CMGF=1';

s = serial('COM5'); 

s.baudrate=9600;
fopen(s);
s.Terminator = 'CR';

fprintf(s,'%s', tx); 
fprintf(s,'%s', tx1); 

BytesAvail=s.BytesAvailable;
    if(BytesAvail > 0), A=fread(s,BytesAvail,'char'); end
A;
sprintf('%c', A)

%%%%%%%%%%%%%%%Send SMS%%%%%%%%%%%%
fprintf(s,'%s', tx5);
fprintf(s,'%s', tx1); 
fprintf(s,'%s', tx3);
fprintf(s,'%s', tx1); 
fprintf(s,'%s', tx4);
fprintf(s,'%s', tx2);
BytesAvail=s.BytesAvailable;
    if(BytesAvail > 0), B=fread(s,BytesAvail,'char'); end
B;

fclose(s)

The error is this

??? Error using ==> serial.fprintf at 144
An error occurred during writing.

Error in ==> message at 20
    fprintf(s,'%s', tx);
>>>