Unable to Erase All Content and Settings

I Unable to 'Erase All Content and Settings'

I recently had to replace my iPhone 6, the Wifi not working, it is greyed out. I tried all the tricks I found here and other sources and nothing worked. Fortunately I had insurance and AT&T replaced the phone.

I got the new phone setup, but now as I try to delete the data of the old phone, I am unable to do so because i get an error when I choose 'Erase All Content...' that says it cant verify the apple ID. It cant do that because I no longer have Cellular service and the Wifi isn't working (the whole reason I am replacing the phone). What options do I have delete this data?