can't receive security code to set up iPhone

So my husband has been using an iPhone 6s and he has upgraded to iPhone 8. Ordered online through our carrier and it arrived today. In preparing to send the old, leased phone back to Sprint, I followed the instructions to backup data and then erase the phone. Bad move! Now I can't seem to activate the new phone because it wants to send a security phone to his cell number...but the phone isn't activated. It is now apparently in Account Recovery status and the latest message is that "status information will be available in 22 hours." We really don't want to have to wait that long! Any suggestions of other measures I can take?