FlyerTalk Evangelist
Join Date: Nov 2018
Location: Istanbul, Turkey
Programs: TK Elite Plus,BAEC GGL,ITA Executive, AFKL Gold,QR Gold,HH Diamond,Bonvoy Gold,ALL Gold
Posts: 14,186
Possible only through your travel agency or TK call center in the same ticket. Be aware that sometimes the system calculates the Economy fare as Y class "highest fare" which can boost the ticket price, which can lead to higher prices compared to an all the way C ticket, so I suggest that you hold the reservation after contacting the call center, recheck it from your inbox and then issue the ticket.