I have Verizon and am replacing my iPhone X and want to know if I am supposed to transfer my old SIM card from the X to the iPhone 12 before migrating information? I have started the migration because one place said not to switch or I won’t have 5G,

You can actually swap the SIM card before or after. You have already started the migration so let it finish and then swap the SIM card from your old iPhone to your new iPhone. Note that whenever and wherever 5G is available then your iPhone 12 will connect to it.

Axel F.

Make sure that you call your carrier and confirm that. It may just be the labeling on the SIM card. Call them.

Axel F.