Lost my phone, need to switch service to "new" phone - not data
So I lost my iphone a week ago, but my roommate gave me his old iphone. I have transferred all of my data (apps, contacts, passwords etc.) over to the new phone.
My problem is that I cannot figure out how to switch my actual service over to the new phone so that I can access my cellular data, make calls, etc.
When I had an account with Sprint, I was able to do this very easily through the website. I don't know if I'm just having trouble navigating the AT&T website or if it's just not possible.
Any help would be greatly appreciate!!