@manukris if your status change was in 2023, then you start FICA from the day after your status change -- you are no-longer a trainee , even if you doing the same job -- because your visa is a work visa. As I said earlier F-1 and OPT together means you are eligible for safe harbor exemption from FICA.
Does this make sense ?
I will circle back if you have any more questions.
