When my flight (DL operated) was delayed out of AMS I called DL first and they told me that I have to use their Contact Us Link too. Until today I never received an answer. After four weeks I decided to call KL and they went right ahead, gave me another reference number (bc. they canīt see DLs reference number and their systems donīt match) and three days later I received an answer. So maybe try to call KL and try to do it over the phone - it worked for me just fine.