Flying with Turkish is usually a very nice experience. The food is excellent and you are well supplied with drinks of all sorts. The lounge in Istanbul is probably one of the best in the world. The ground service is a problem. Not only have I met with ignorant and impertinent staff but I´ve also been lied at.
When I recently tried to book a flight with my bonus miles which you according to their own instructions shall do through customer services in Istanbul , I was twice advised to do this in Stockholm at two different contact points that both directed me back to Istanbul. When I complained to customer services and asked what is the right procedure the answer was that I should do that through Istanbul - which obviously the staff in Istanbul is not very interested to help you with. A catch 22 quite clearly. I had to give up in the end.