A KLM Airlines Reservations Number is the telephone number used by KLM Airlines and they don't want you to have this. They want you to contact them directly and tell them that you wish to get in touch with them, and not directly use the telephone number. It would also be a good idea to call the same number several times, to double check if the telephone is still active. If the KLM Airlines Reservation Number is active then the phone number is working but if it is not the KLM Airlines Reservation Number is most likely been switched off.

https://travelwithronny.blogspot.com/2020/03/finding-your-klm-airlines-reservations.html