My a80 have issue with Siam card. always asking me to upgrade.

@koomsonyeboah you have to make sure that you have a working SIM card. Check with your service provider first. Any troubleshooting relies on you having a working SIM card.

After that you want to follow the Samsung Flowchart. Power for the SIM card comes from the Sub board (daughter board). There are no schematic for that. You need to rule it out by testing the other components. If they are okay, replace the daughter board.

While you work on your phone, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has the same problem as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.