Your phone might support using an eSIM (embedded SIM card), in addition to any physical SIM card(s). Contact your carrier for details.
If your carrier provided instructions to activate an eSIM, follow their instructions.
To activate the eSIM yourself:
Tap Download new SIM to get and set up the eSIM, then follow onscreen instructions.
If you don't see this option, contact your carrier to confirm if your phone supports eSIMs and to get activation instructions.
Insert the SIM tool into the tray hole and gently push to pop it out.

Insert or remove the cards as needed.
To use one SIM card:

If you're using two SIM cards, turn the tray over and insert (gold contacts up) the second card.

To see if your phone supports two phsyical SIM cards, go to Settings > About phone > Device details. If you see SIM status (sim slot 1) and SIM status (sim slot 2), then you can use two physical SIMs.
Push the tray back into the phone.

You may need to erase your eSIM:
When you erase an eSIM, you remove the following capabilities from the phone:
Erasing the eSIM does not cancel your mobile data services. To cancel your services, contact your carrier.
To erase an eSIM:
To restore an eSIM you erased, contact your carrier.
If you’re having problems, try these troubleshooting steps.