When you own it more than a month, cancel it now, you will get a part of your subscription back. You cannot cancel in the first month. When you do need to travel, do not cancel. When you cancel Flex Dalvrij, the subscription stops at the same moment.

I understand nutz is now asking-cautious-very good! if s/he has to do NOW or later -the answer has been given: it will ALWays become effective at that moment-you cannot anticipate.

(Thats how I did it whilst in transit at a foreign airport some days ago-now away for long holiday.

It depends on if you still want to use your subscription between now and December 14th. If you cancel now it will end now and you cannot use it anymore, you cannot cancel using a date in the future. So if you still want to use your subscription for travel, cancel after your last travel. If you are not using it anymore now until December 14, cancel now.