One hint from my side: if possible, avoid calling the call center in Istanbul, they are mostly clueless. I called the Italian line instead (they answered from Romania) and everyone was so friendly and knew the ticket rules very well: they re-issued my new ticket in 24 hours, opening an award seat on a flight were award seats were not available anymore. TK had previoulsy cancelled my flight out of Riyadh and I asked the Italian line to re-book me on a different date & departure point (within the same geographical area of the original ticket)