My flights in September with LH and LX to Greece got cancelled. I was automatically rebooked, but my outbound flight now included an overnight connection, and my inbound flights had the two segments inverted timewise (i.e. in the absence of a time machine, that wasn't going to work). I called the helpline and after a short five minute wait the helpful operator rebooked me into much more acceptable choices. Note that my flights had originally been booked via an OTA.