Here is Turkish Airlines second response. Now it's not Singapore Airlines fault but the agency I booked my flight with
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Dear,
Your file has been re-evaluated by our side.
In relation with your concern, we would like to kindly inform you that your reservation is a third party booking and the you are supposed to be informed about your flights by your agency. If the agency sent you the details of your reservation via e-mail or sms, it could be clearly shown that this flight is operated with another airline. Of course, we do not know whether the agency send you the details of your reservation or informed you that this flight in not Turkish Airlines. Besides, we have seen that you were transferred to correct desks to give you direct you to correct place.
As a conclusion, we could not determine an irregularity that can help us to assist you. Unfortunately, as we stated before, the check-in transaction must be made for the other airline, if you are not giving a boarding pass for it.
We submit the above to your information and would like to state our regret at these practices causing you dissatisfaction.
Sincerely yours,
Pınar A.
Turkish Airlines Inc.
Customer Contact Center