Make sure both iPhones are connected to Wi-Fi and signed in with the same Apple ID if using eSIM Quick Transfer
On the new iPhone, go to Settings
Tap Cellular or Mobile Data
Tap Add eSIM
Tap Transfer From Nearby iPhone
Follow the on-screen instructions on both iPhones
Approve the transfer on the old iPhone when prompted
Wait for the eSIM to activate on the new iPhone
If Quick Transfer is not available, contact your carrier for an eSIM activation QR code or activation details
On the new iPhone, go to Settings
Tap Cellular or Mobile Data
Tap Add eSIM
Tap Use QR Code
Scan the QR code provided by your carrier
Follow the prompts to finish activation
Remove the eSIM from the old iPhone only after the new iPhone is working
Restart the new iPhone if the cellular service does not activate immediately