what to do if data transfer interrupted during set up of new iPhone

This does not help. The resources do not tell us how to re-establish the transfer if it was accidentally cancelled or interrupted mid-migration. There's no way to reset the new phone to go back to the original state and start over.

Hey pd1993,

Thanks for using Apple Support Communities! I understand your data transfer was interrupted. I definitely want to make sure you're able to get your new iPhone 11 up and running with all your content available. I am happy to help provide some help.

I recommend taking a look at the resource below, as this goes over all your options for transferring data to your new iPhone from your previous device, and how to get them started.

Transfer data from your previous iOS device to your new iPhone, iPad, or iPod touch

Thanks again, and have a great day!