Assigning a seat and paying for it are 2 separate transactions. Normally legacy airlines issue a document called EMD - Electronic Miscellaneous Document to charge for the seat. If you have not been charged (so no EMD was issued), the airline will most likely cancel your seat assignment. AC is on Amadeus and TK on IBM Res3/Troy. Transfer of data between systems is very often inaccurate. I would not rely on cowtool (which I guess in the background uses Amadeus API), but rather check status on TK App which is the most solid source of information for TK flights.