Problem when modifying data from an Array

I have an array of statistics where I keep the statistics of each level, letter.

   ContentValues valors = new ContentValues();
        valors.put("user_id", id);
        valors.put("letra", "b");
        valors.put("jugadas", 0);
        valors.put("errores", 0);
        valors.put("acertada", 0);
        valors.put("tiempo", 0);

        baseDatos.getWritableDatabase().insert("estadisticas", null, valors);

The problem I have is I modify that data. Although the increase does not change the number 0 put initially.

   public void incrementarJugadas(String letra, int user_id) {

        String sql = "UPDATE Estadisticas SET jugadas= jugadas+1 WHERE user_id= " + user_id + " AND letra='" + letra+"'";
        getReadableDatabase().execSQL(sql);
        this.getWritableDatabase().insert("estadisticas", null, valores);}


}

Does anyone know what's wrong? I have another previous level, where I use the same mechanism and it does work, but in this, for more times than I call increasingJugadas, it always returns the 0 that I put in initial.