400 bad request on send SMS

Hi Support

I'm using javascript SDK for send SMS feature and app is under development mode. I'm getting 400 bad request when I post request for Send SMS. Here is my code

function send_sms($phone,$message){        

          $json_data = {            
                    "from": {
                            "phoneNumber": "+1000000000"
                    },
                    "to": [{
                            "phoneNumber": $phone
                    }],
                    "text": $message    };
          platform.post('/account/~/extension/~/sms',$json_data
          ).then(function(response) {
              console.log(response.json()); 
              //alert('Success: ' + response.json().id);
          })
          .catch(function(e) {
              //alert('Error: ' + e.message);
          }); 
    }

Please let me know how to resolve this issue??

Thank you!