SIM Card Swap
Must I remove old sim card and place in new iPhone after performing Quick Start? New phone cannot make calls.
iPhone 12 Pro Max, iOS 14
Depends entirely on whether you got the phone locked to a provider with a SIM already installed or a SIM free phone that arrived without one.
You cannot activate a new phone with no SIM in it so I assume it came with one in which case call your network provider help desk.