It sounds like you're looking more for "how can I be a good seller in the face of a bad situation" advice than Nokia troubleshooting advice.
And that's fine. Something to keep in mind when selling products over the internet is that you need to look out for yourself; there are a lot of folks out there who will try to complain about something you sold them just to see if they can't squeeze a few bucks out of you. I'm not necessarily saying that's the case here, but it's certainly something to consider when dealing with this guy. Since the E70's a pretty new phone, it's almost certainly still under a Nokia manufacturer warranty somewhere. Suggest that your buyer give Nokia a call get the phone serviced. Alternately, you could call them yourself and say that you need to send a defective E70 in for service simply giving his name and address as the information for your service request. Make sure that it's okay to ship to and from Canada, and if it's not, find out which Nokia division/phone number to contact that will. Once you have that taken care of, contact him and let him know where he needs to send the phone.
If he's stubborn and refuses to do any of that, simply offer him a full refund in exchange for sending the phone back to you. Wait to send his refund until you have the phone back in your hands, and can verify that the defects he described are actually present (in which case, you'll want to get that phone serviced by Nokia yourself before re-selling it). If he's screwing with you, he very likely will not want to do this -- you're either calling his bluff, or righting a wrong that inexplicably occurred during shipping. Don't agree to pay his postage, either -- it's pretty standard policy that the buyer pay postage for a return when dealing with transaction between individuals.
