binding parameters with SQL update query

how can I bind the following parameters in my query? does the "?" count as the parameters and are parameters are positioned in order?

Here's my code:

case 'setpassword':  
if(isTheseParametersAvailable(array('phone_number','password'))){  
$phone_number = $_POST['phone_number'];  
$password = SHA1($_POST['password']);
 

$stmt = $conn->prepare("UPDATE users SET password = ? WHERE phone_number= ? ");  
$stmt->bind_param("ss",$password,$phone_number);  
$stmt->execute();  
$stmt->store_result();  
   if($stmt->num_rows > 0){  
   $stmt->bind_result($id,$phone_number,$password);  
   $stmt->fetch();  
   $user = array(  

   'phone_number'=>$phone_number,
   'password'=>$password  

   );   

   $response['error'] = false;   
   $response['message'] = 'Password set successful';   
   $response['user'] = $user;   
   }  
   else{  
   $response['error'] = true;   
   $response['message'] = 'Password set error';  
   }  
}  
break;

my code has no errors but it cannot find any data.