I'm glad to share a successful claim of compensation from TK recently. My trip on 2 Jan 2016 was from OTP-IST-DOH and the first leg was delayed by more than 3 hours, causing me to miss my connecting flight and I was practically going in circles before getting to the lounge and spent the next 5 hours sorting out the mess (which include rebooking DOH-SIN flights)
There was a QR flight that departs to DOH 2 hours after I have landed at IST and I practically have to stand my ground and ask for them to rebook on this flight as the next direct flight to DOH will be some 18 hours later. The lounge staff called an internal line for help but it seems their ticketing department was unwilling to rebook me on anything else except on their own TK metal citing mine was a award ticket even when I told them I was willing to sit in Y when i was ticketed in J. They refused to rebook me to SIN as well as I was supposed to catch a flight from DOH to SIN because the flight distance was greater than my booked ticket. I was also denied the usage of a phone though their CS manual states otherwise and was told to connect on lounge Wifi to make calls. Eventually I was put up in a hotel for half a day and rebooked on the next TK flight out which was 18 hours later, hence reaching DOH with a massive delay and managed to take another flight back to SIN.
My bags did not make it back with me too, only resurfacing nearly 3 days later. I lodged a complaint when I got back and cited EU261 and made my claim for EUR400 and reimbursement for IDD calls incurred with proof of bill provided and their first 3 replies was to reject my claim outright citing safety threat with incoming flight to OTP. When I pressed them for proof of the safety threat, they then changed their reason to that on 1st/2nd Jan, most flights were delayed or canceled due to intensive snow, which is considered unsafe to operate the flight.
Nearly giving up at this stage, I reviewed the correspondences and I realise they keep using the incoming flight as a reason to reject my claim. Hence I framed my final reply to them that my beef with them was that they did not live up to their CS standards by not rebooking me on the next available flight on QR despite me begging them for it at the lounge and the flight actually took off with minimal delay, hence they cannot claim weather or safety issues as a means to reject my claim. If they had rebooked me before I had arrived in IST (since I had >3 hours delay) or while I was in the lounge with 2 hours before QR flight departs, I would not be arguing with them now.
I didn't hear from them for like 2 weeks and had proceeded to file a claim with a claims specialist site which actually rejected my claim citing snowfall too. I was then surprised to receive TK's reply a day later apologising for misinformation and incomplete result for my feedback and offered me my full EU261 compensation and little extra compensation for my IDD calls charges in the form of a EMD and was told to contact a local sales office which I did and is now waiting for the money via bank transfer. Persistence is key probably? And also framing your argument well instead of giving them an open-ended case might work better.