The issue could be one of several variables.
Does this happen in a particular area or everywhere.
Can you as a process of elimination try your sim card in another phone and then another sim card in your phone and then see what happens.
A person can reset their network connections via Settings > General Management > Reset > Reset Network Connections.
There is a diagnostic tool in your Samsung Members App under the GetHelp section.
A Samsung Service Centre can check out the phone for faults.
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.