Easy now. All of us !
Yesterday I was told on the phone that KCI don't accept the 90-day report by mail any more. Hence I quickly posted my first message on this subject.
Today I got the receipt for my last report to January 9 with no mention that they should not accept my reports by mail anymore. The receipt was dated January 8.
I will ignore what I was told on the phone yesterday and send my next report by mail again in April. Then I will have plenty of time to wait before I shall go and apply for a new extension of stay in the beginning of May