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 🌈
My advice comes from being a UK Samsung Phone Owner.
I have no affiliation with Samsung.
Current Phone ~
Samsung Note 10 Plus 5G _256Gb >_ Samsung One Ui 2.5/ Android 10.