true, hoowever also true that not everyone want to spend hours on the phone with a call center for something that should take no time directly on the website if it worked well...(hope sooner or later TK will upgrade the website to be functional...)

the suggestion is anyway to go to the airport to do the upgrade only the day fo departure, not weeks before as they likely can do nothing if you go in advance.

certainly the last day you get your luck depending on the eventual booking availability, but unless the biz class is fully fully booked or even overbooked, it would likely not an issue to enjoy the upgrade