Does your sim card work in another phone ?
Does another sim card work in your phone ?
Try removing your sim card , gently wipe the chip and reinsert.
Also try resetting the Network Settings in the phone.
🌈 Stay Safe 🌈
Current Phone ~
Samsung Note 20 Ultra 5G SM-9820 _256Gb SnapDragon 865+
Samsung One Ui 2.5/ Android 10.