Frustrated for booking with a Pet

Hello everyone I’m trying to book for a flight with a pet in cabin. From the information I gathered is that I have to call them before I book for the flight to make sure there are no pets on the flight. I called them over 6 times now and everyone is telling me a different thing from their customer service line! I’m so frustrated because I want to book the flight early. Through the app there are some flights that won’t let me add the pet and it says the service cannot be done online. And some flights on different days allows me to add the pet and choose the seats as well.. I don’t understand how am I supposed to book for a flight and add a pet in cabin. It got to a point when I was able to add the pet to the booking and before I pay I called customer service and they said both flights has a cat in it but they can’t confirm or deny now that my pet will be approved or not… i asked if it’s possible that it’s the pet I added? And he said to just go through the booking and pay and know later if it will be approved or not even though there’s already a pet booked in both flights. Did anyone go through a similar situation? I went to their office and they refused to book me a one way ticket and insisted on me buying a return ticket even though I still don’t know how long I will be staying with my husband and if I even want to return with turkish airlines again.