I searched over net and found that the internal name of a field or column in SharePoint list might be different.
Then I searched how to know the internal name of a field in sharepoint list and found the solution.
This is a powershell command which list out all the field with their internal name.
Here is the command for powershell:
$web = Get-SPWeb http://sharepointcafe:80
$list = $web.Lists[“MyListName”]
$list.fields | select Title, InternalName, Hidden, CanBeDeleted | sort title | ft -AutoSize
You might also get the internal names by client object model code.