Seats assigned automatically 2wks prior departure?

We are a family of 5, 2 adults traveling with 3 small children. On the way here (Bkk) we got seats sitting together automatically on web check in. Now I just opened TK app and saw we already have seats assigned to us and we are on the opposite sides of the plane (2 + 3). Departure in less than 2 weeks. What happened? I dont understand.

Anything to do? Call customer service and beg? And yes, the plane seems empty, just a few rows are occupied and buying seats for us is 500€ total. Which is a bit too much for us.