I called FedEx and they won't let you change delivery address or hold at a FedEx location until after they make one delivery attempt.
If you won't be home tomorrow and want your phone before Monday, you'll need to leave a note for your delivery driver asking to leave the package without a signature. Not worth the risk for me.
I kind of get why they won't allow changes of address, but it seems silly to disallow holding at a FedEx location. I have to show up and present my ID to get the package so it seems much more secure from the AT&T/FedEx perspective than just leaving it on my doorstep but whatever. Monday it is, I guess