Drop table if exits not works on SQlite database in Android

I have a SQLite Database on Database, I store that database from PHP Server, I crete database, If I add new values to PHP databse it's appear on my android device, but...

MY PROBLEM

When I delete one value to Server database, on my device not delete from sqlite database, database is not updated only when I delete values from php database but yes works when I add values...

code DDBB

public class BBDD extends SQLiteOpenHelper
{
    private static final String KEY_ID = "id";

 String crear = "CREATE TABLE types(KEY_ID INTEGER PRIMARY KEY," +
                                            "value TEXT) ";


    public BBDD (Context contexto, String nombre, CursorFactory factory,
                 int version)
    {
        super(contexto, nombre, factory, version);
    }

    public void onCreate (SQLiteDatabase db)
    {
        db.execSQL(crear);
    }

    public void onUpgrade (SQLiteDatabase db, int versionAnt, int versionNue)
    {
        db.execSQL("DROP TABLE IF EXISTS types");
        db.execSQL(crear);

    }

Why not works DROP TABLE IF EXITS?

Any suggestions?