I had a horrible costumer service experience. The kiwi app had a bug when I was booking my tickets: when I entered a date of birth, in the end it always said one day less (5th instead of the 6th). To edit that after would cost 30e per passenger and since I was booking for more people it would be a lot. So I called them (costing me money) to fix it and they did change it- again to a wrong date. I really don't need this kind of stress before my flights...