As a process of elimination try your sim card in another phone and then see what happens which will help rule out if your sim card is at fault and may need replacing.
Also if you can please try another different sim card in your phone and see what happens @Luchia
A Samsung Service Centre can check out the phone.
I wish you all the best.
Daily Driver > Samsung Galaxy s²² Ultra 256Gb in Phantom Black.
The advice I offer is my own and does not represent Samsung’s position.
I have no affiliation with Samsung.